View source for Firefox

{{Short description|Web browser made by Mozilla}}
{{Hatnote group|
{{About|the web browser}}
{{Redirect|Phoenix (web browser)|the 1990s web browser developed at the University of Chicago|Phoenix (tkWWW-based browser)}}
}}
{{Pp-move|small=yes}}
{{Use American English|date=May 2020}}
{{Use mdy dates|date=January 2024}}
{{Infobox software
| name = Firefox <!-- Technical name; do not change -->
| title = Firefox
| logo = Firefox_logo,_2019.svg <!-- Please do not change to that fire-only logo. That logo is for the Firefox brand of products, not the Firefox browser. https://blog.mozilla.org/opendesign/firefox-the-evolution-of-a-brand/ -->
| logo size = 125px
| logo_caption = [[Firefox logo|Logo]] used since October 2019
| logo_alt = Firefox logo
| screenshot = Firefox 145.0 opening Wikipedia article on Linux screenshot.webp
| caption = Firefox 145.0 [[64-bit computing|(64-bit)]] running on the [[OpenSUSE]] operating system
| developer = {{ubl
  |[[Mozilla Foundation]] and its contributors
  |[[Mozilla Corporation]]
}}
| released = {{Start date and age|2004|11|9}}
| ver layout = stacked
| repo = <!-- Automatically filled; do not modify. -->
| programming language = [[C++]], [[JavaScript]], [[HTML]], [[C (programming language)|C]], [[Rust (programming language)|Rust]], and others<ref>{{cite news |url=https://www.infoworld.com/article/3165424/web-browsers/mozilla-binds-firefoxs-fate-to-the-rust-language.html |title=Mozilla binds Firefox's fate to the Rust language |last=Yegulalp |first=Serdar |date=February 3, 2017 |work=InfoWorld |access-date=August 19, 2017 |archive-url=https://web.archive.org/web/20170819063448/http://www.infoworld.com/article/3165424/web-browsers/mozilla-binds-firefoxs-fate-to-the-rust-language.html |archive-date=August 19, 2017 |url-status=live}}</ref><ref>{{Cite web |title=The Mozilla Firefox Open Source Project on Open Hub: Languages Page |url=https://www.openhub.net/p/firefox/analyses/latest/languages_summary |access-date=October 15, 2021 |website=openhub.net |archive-date=October 7, 2021 |archive-url=https://web.archive.org/web/20211007234007/https://www.openhub.net/p/firefox/analyses/latest/languages_summary |url-status=live}}</ref>
| operating system = {{ubl
  |[[Linux]]
  |[[macOS Sierra]] or later
  |[[Windows 7]] or later
  |[[Windows Server 2008 R2]] or later
  |[[Android Oreo]] or later<ref name="Firefox for Android upgrade FAQs">{{cite web |url=https://support.mozilla.org/en-US/kb/firefox-android-upgrade-faqs?redirectslug=firefox-preview-upgrade-faqs&redirectlocale=en-US |title=Firefox for Android upgrade FAQs |access-date=August 16, 2020 |archive-date=August 12, 2020 |archive-url=https://web.archive.org/web/20200812152044/https://support.mozilla.org/en-US/kb/firefox-android-upgrade-faqs?redirectslug=firefox-preview-upgrade-faqs&redirectlocale=en-US |url-status=live}}</ref>
  |[[iOS 15]] or later
  |[[iPadOS 15]] or later
}}
| included with = Various [[Unix-like]] operating systems
| engines = [[Gecko (software)|Gecko]], [[Quantum (Mozilla)|Quantum]], and [[SpiderMonkey]]; [[WebKit]] on iOS/iPadOS
| language count = 97
| language footnote = <ref name="languages" />
| genre = [[Web browser]]
| license = [[MPL 2.0]]<ref>{{cite web |url=https://www.mozilla.org/en-US/about/legal/eula/ |title=Mozilla |access-date=October 20, 2014 |archive-url=https://web.archive.org/web/20141021035640/https://www.mozilla.org/en-US/about/legal/eula/ |archive-date=October 21, 2014 |url-status=live}}</ref><ref name="Licensing-Policies" />
| website = {{url|https://www.firefox.com/|firefox.com}}
| standard = 
| AsOf = 
}}

'''Mozilla Firefox''', or simply '''Firefox''', is a [[Free and open-source software|free and open-source]]<ref name="LWNtrademark">{{cite web |url=https://lwn.net/Articles/118268/ |title=Debian and Mozilla – a study in trademarks |date=January 10, 2005 |website=[[LWN.net]] |archive-url=https://web.archive.org/web/20170801163012/https://lwn.net/Articles/118268/ |archive-date=August 1, 2017 |access-date=September 14, 2011 |author=Corbet, Jonathan |url-status=live}}</ref> [[web browser]] developed by the [[Mozilla Foundation]] and its subsidiary, the [[Mozilla Corporation]]. It uses the [[Gecko (software)|Gecko]] [[Browser engine|rendering engine]] to display web pages, which implements current and anticipated web standards.<ref>{{cite web |url=http://download-firefox.org/spread-firefox/gecko-layout-engine-and-mozilla-firefox/ |title=Gecko Layout Engine |date=July 17, 2008 |publisher=download-firefox.org |archive-url=https://web.archive.org/web/20100615131607/http://download-firefox.org/spread-firefox/gecko-layout-engine-and-mozilla-firefox/ |archive-date=June 15, 2010 |access-date=May 10, 2012}}</ref> The software is available for [[Microsoft Windows|Windows]], [[macOS]], and [[Linux]] systems, with unofficial ports for other platforms, as well as a [[Mobile web|mobile]] version for [[Android (operating system)|Android]] (see [[Firefox for Android]]) and [[iOS]]. 

Firefox is the [[spiritual successor]] of [[Netscape Navigator]], as the [[Mozilla]] community was created by [[Netscape]] in 1998, before its acquisition by [[AOL]].<ref>{{cite news |url=http://www.cbc.ca/technology/technology-blog/2008/02/curtains-for-netscape.html |title=Curtains for Netscape – Tech Bytes |last=Jay |first=Paul |date=February 28, 2008 |publisher=CBC News |access-date=June 26, 2015 |archive-url=https://web.archive.org/web/20150705110100/http://www.cbc.ca/technology/technology-blog/2008/02/curtains-for-netscape.html |archive-date=July 5, 2015 |url-status=live}}</ref> Firefox was created in 2002 under the codename "Phoenix" by members of the Mozilla community who desired a standalone browser rather than the [[Mozilla Application Suite]] bundle. During its [[Software release life cycle#Beta|beta]] phase, it proved to be popular with its testers and was praised for its speed, security, and add-ons compared to [[Microsoft]]'s then-dominant [[Internet Explorer 6]]. It was released on November 9, 2004,<ref>{{cite web |url=https://news.bbc.co.uk/1/hi/technology/3993959.stm |title=Firefox browser takes on Microsoft |date=November 9, 2004 |work=[[BBC News]] |url-status=live |archive-url=https://web.archive.org/web/20171220113953/http://news.bbc.co.uk/2/hi/technology/3993959.stm |archive-date=December 20, 2017}}</ref> and challenged [[Internet Explorer]]'s dominance with 60 million downloads within nine months.<ref>{{cite web |url=https://news.bbc.co.uk/2/hi/business/4508897.stm |title=The assault on software giant Microsoft |last=Weber |first=Tim |date=May 9, 2005 |work=[[BBC News]] |url-status=live |archive-url=https://web.archive.org/web/20170925233936/http://news.bbc.co.uk/2/hi/business/4508897.stm |archive-date=September 25, 2017}}</ref> In November 2017, Firefox began incorporating new technology under the code name "[[Quantum (Mozilla)|Quantum]]" to promote [[Parallel computing|parallelism]] and a more intuitive [[user interface]].<ref>{{Cite web |url=https://blog.mozilla.org/blog/2017/11/14/introducing-firefox-quantum/ |title=Introducing the New Firefox: Firefox Quantum |last=Mayo |first=Mark |date=November 14, 2017 |website=The Mozilla Blog |archive-url=https://web.archive.org/web/20180627114050/https://blog.mozilla.org/blog/2017/11/14/introducing-firefox-quantum/ |archive-date=June 27, 2018 |access-date=May 26, 2018}}</ref>

The current version of Firefox is available for [[Windows 10]] or later versions of Windows, as well as macOS, and Linux. Its unofficial ports are available for various [[Unix]] and [[Unix-like]] operating systems, including [[FreeBSD]],<ref name="FreeBSD ports2">{{cite web |title=FreeBSD ports |url=https://svnweb.freebsd.org/ports/head/www/firefox/ |url-status=live |archive-url=https://web.archive.org/web/20190323104221/https://svnweb.freebsd.org/ports/head/www/firefox/ |archive-date=March 23, 2019 |access-date=March 24, 2018}}</ref> [[OpenBSD]],<ref name="OpenBSD ports2">{{cite web |title=OpenBSD ports |url=http://cvsweb.openbsd.org/cgi-bin/cvsweb/ports/www/mozilla-firefox/ |url-status=live |archive-url=https://web.archive.org/web/20190120074628/http://cvsweb.openbsd.org/cgi-bin/cvsweb/ports/www/mozilla-firefox/ |archive-date=January 20, 2019 |access-date=March 24, 2018}}</ref>, [[NetBSD]],<ref name="NetBSD pkgsrc2">{{cite web |title=NetBSD pkgsrc |url=http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/www/firefox/ |url-status=live |archive-url=https://web.archive.org/web/20181101015707/http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/www/firefox/ |archive-date=November 1, 2018 |access-date=October 31, 2018}}</ref>and other operating systems, such as [[ReactOS]]. It is the default, pre-installed browser on [[Debian]], [[Ubuntu]], and some other Linux distros. Firefox is also available for [[Android (operating system)|Android]] and [[iOS]]. However, as with all other iOS web browsers, the iOS version uses the [[WebKit]] layout engine instead of Gecko due to platform requirements. An optimized version was also available on the [[Amazon Fire TV]] as one of the two main browsers available with Amazon's [[Amazon Silk|Silk Browser]]<ref>{{Cite web |title=Firefox for Fire TV |url=https://www.amazon.com/Mozilla-Firefox-for-Fire-TV/dp/B078B5YMPD |url-status=live |archive-url=https://web.archive.org/web/20200707103351/https://www.amazon.com/Mozilla-Firefox-for-Fire-TV/dp/B078B5YMPD |archive-date=July 7, 2020 |access-date=July 17, 2020 |website=Amazon}}</ref> until April 30, 2021, when Firefox would be discontinued on that platform.

Firefox usage share grew to a peak of 32.21% in November 2009,<ref name="StatCounter">{{cite web |url=https://gs.statcounter.com/browser-market-share/desktop/worldwide/#monthly-200901-201301 |title=Desktop Browser Market Share Worldwide (Jan 2009 – Jan 2013) |last=StatCounter |website=gs.statcounter.com |access-date=October 23, 2021 |url-status=live |archive-date=October 11, 2017 |archive-url=https://web.archive.org/web/20171011022101/https://gs.statcounter.com/browser-market-share/desktop/worldwide#monthly-200901-201301}}</ref> with [[Firefox 3.5]] overtaking [[Internet Explorer 7]], although not all versions of Internet Explorer as a whole;<ref>{{Cite web |url=https://gs.statcounter.com/#browser_version-ww-weekly-200827-200951 |title=StatCounter Global Stats – Browser, OS, Search Engine including Mobile Usage Share |website=StatCounter Global Stats |access-date=July 14, 2018 |archive-url=https://archive.today/20120526/http://gs.statcounter.com/%23mobile_browser-ww-monthly-201012-201111-bar#browser_version-ww-weekly-200827-200951 |archive-date=May 26, 2012 |url-status=live}}</ref><ref>{{cite web |url=https://gs.statcounter.com/#browser_version-ww-monthly-200902-201006 |title=StatCounter global stats – Top 12 browser versions |publisher=StatCounter |access-date=March 12, 2010 |archive-url=https://archive.today/20120526/http://gs.statcounter.com/%23mobile_browser-ww-monthly-201012-201111-bar#browser_version-ww-monthly-200902-201006 |archive-date=May 26, 2012 |url-status=live}}</ref> its usage then declined in competition with [[Google Chrome]].<ref name="StatCounter" /> {{As of|2025|02}}, according to [[StatCounter]], it had a 6.36% [[Usage share of web browsers|usage share]] on traditional PCs (i.e. as a desktop browser), making it the fourth-most popular PC web browser after Google Chrome (65%), [[Microsoft Edge]] (14%), and [[Safari (web browser)|Safari]] (8.65%).<ref>{{Cite web |title=Desktop Browser Market Share Worldwide |url=https://gs.statcounter.com/browser-market-share/desktop/worldwide/#monthly-202502-202502-bar |access-date=March 5, 2025 |website=StatCounter Global Stats }}</ref>

== History ==
{{See also|Firefox early version history|Firefox version history}}
The project began as an experimental branch of the [[Mozilla Application Suite|Mozilla project]] by [[Dave Hyatt]], [[Joe Hewitt (programmer)|Joe Hewitt]], and [[Blake Ross]]. They believed the commercial requirements of [[Netscape]]'s sponsorship and developer-driven [[feature creep]] compromised the utility of the Mozilla browser.<ref>{{cite web |last=Goodger |first=Ben |author-link=Ben Goodger |title=Where Did Firefox Come From? |work=Inside Firefox |publisher=MozillaZine Weblogs |date=February 6, 2006 |url=http://weblogs.mozillazine.org/ben/archives/009698.html |archive-url=https://web.archive.org/web/20110623034401/http://weblogs.mozillazine.org/ben/archives/009698.html |archive-date=June 23, 2011 |access-date=January 7, 2012}}</ref> To combat what they saw as the [[Mozilla Suite]]'s [[software bloat]], they created a standalone browser, with which they intended to replace the Mozilla Suite.<ref name=secrets>{{cite book |last=Yeow |first=Cheah Chu |year=2005 |title=Firefox Secrets |url=https://books.google.com/books?id=sfciobmzOOcC |publisher=SitePoint Pty Ltd |isbn=978-0-9752402-4-3 |access-date=December 12, 2015 |archive-url=https://web.archive.org/web/20190323104230/https://books.google.com/books?id=sfciobmzOOcC |archive-date=March 23, 2019 |url-status=live}}</ref> Version 0.1, named Phoenix, was released on September 23, 2002.<ref>{{Cite magazine |url=https://www.wired.com/2012/09/happy-birthday-firefox-the-little-web-browser-that-could-turns-10/ |title=Happy Birthday, Firefox: The Little Web Browser That Could Turns 10 |last=Gilbertson |first=Scott |date=September 24, 2012 |magazine=Wired |access-date=September 20, 2019 |archive-url=https://web.archive.org/web/20170805143306/https://www.wired.com/2012/09/happy-birthday-firefox-the-little-web-browser-that-could-turns-10/ |archive-date=August 5, 2017 |url-status=live}}</ref> On April 3, 2003, the [[Mozilla Foundation|Mozilla Organization]] announced that it planned to change its focus from the Mozilla Suite to Firefox and [[Mozilla Thunderbird|Thunderbird]].<ref>{{cite web |url=https://www-archive.mozilla.org/roadmap/roadmap-02-Apr-2003.html |title=mozilla development roadmap |last1=Eich |first1=Brendan |author-link=Brendan Eich |last2=Hyatt |first2=David |author-link2=Dave Hyatt |date=April 2, 2003 |publisher=[[Mozilla]] |access-date=August 2, 2009 |archive-url=https://web.archive.org/web/20090410050040/http://www-archive.mozilla.org/roadmap/roadmap-02-Apr-2003.html |archive-date=April 10, 2009 |url-status=live}}</ref>

[[File:Phoenix 0.1.png|thumb|left|Screenshot of Phoenix 0.1 on [[Windows XP]] ]]
The Firefox project has undergone several name changes.<ref>See:
*{{cite web |url=https://www.mozilla.org/projects/firebird/0.1-release-notes.html |title=Phoenix 0.1 (Pescadero) release Notes and FAQ |date=May 28, 2003 |website=mozilla.org |access-date=February 26, 2018 |archive-url=https://web.archive.org/web/20030528145420/http://www.mozilla.org/projects/firebird/0.1-release-notes.html |archive-date=May 28, 2003}}
*{{cite web |url=https://www.mozilla.org/projects/firebird/0.2-release-notes.html |title=Phoenix 0.2 (Santa Cruz) release Notes and FAQ |date=December 3, 2003 |website=mozilla.org |access-date=February 26, 2018 |archive-url=https://web.archive.org/web/20031203013057/http://www.mozilla.org/projects/firebird/0.2-release-notes.html |archive-date=December 3, 2003}}
*{{cite web |url=https://www.mozilla.org/projects/firebird/0.3-release-notes.html |title=Phoenix 0.3 (Lucia) release Notes and FAQ |date=December 3, 2003 |website=mozilla.org |access-date=February 26, 2018 |archive-url=https://web.archive.org/web/20031203013057/http://www.mozilla.org/projects/firebird/0.3-release-notes.html |archive-date=December 3, 2003}}
*{{cite web |url=https://www.mozilla.org/projects/firebird/0.4-release-notes.html |title=Phoenix 0.4 (Oceano) Release Notes and FAQ |date=December 3, 2003 |website=mozilla.org |access-date=February 26, 2018 |archive-url=https://web.archive.org/web/20031203013057/http://www.mozilla.org/projects/firebird/0.4-release-notes.html |archive-date=December 3, 2003}}
*{{cite web |url=https://www.mozilla.org/projects/firebird/0.5-release-notes.html |title=Phoenix 0.5 (Naples) Release Notes and FAQ |date=December 3, 2003 |website=mozilla.org |access-date=February 26, 2018 |archive-url=https://web.archive.org/web/20031203013057/http://www.mozilla.org/projects/firebird/0.5-release-notes.html |archive-date=December 3, 2003}}
*{{cite web |url=https://www.mozilla.org/projects/firebird/0.6-release-notes.html |title=Mozilla Firebird 0.6 Release Notes and FAQ |date=December 3, 2003 |website=mozilla.org |access-date=February 26, 2018 |archive-url=https://web.archive.org/web/20031203013057/http://www.mozilla.org/projects/firebird/0.6-release-notes.html |archive-date=December 3, 2003}}
*{{cite web |url=https://www.mozilla.org/projects/firebird/0.6.1-release-notes.html |title=Mozilla Firebird 0.6.1 Release Notes and FAQ |date=December 3, 2003 |website=mozilla.org |access-date=February 26, 2018 |archive-url=https://web.archive.org/web/20031203013057/http://www.mozilla.org/projects/firebird/0.6.1-release-notes.html |archive-date=December 3, 2003}}
*{{cite web |url=https://www.mozilla.org/projects/firebird/0.7-release-notes.html |title=Mozilla Firebird 0.7 Release Notes |date=October 28, 2003 |website=mozilla.org |access-date=February 26, 2018 |archive-url=https://web.archive.org/web/20031028041058/http://www.mozilla.org/projects/firebird/0.7-release-notes.html |archive-date=October 28, 2003}}</ref> The nascent browser was originally named Phoenix, after the [[phoenix (mythology)|mythical bird]] that rose triumphantly from the ashes of its dead predecessor (in this case, from the "ashes" of [[Netscape Navigator]], after it was sidelined by Microsoft Internet Explorer in the "[[First Browser War]]"). Phoenix was renamed in 2003 due to a trademark claim from [[Phoenix Technologies]]. The replacement name, Firebird, provoked an intense response from the [[Firebird (database server)|Firebird]] database software project.<ref>{{cite web |title=Mozilla browser becomes Firebird |publisher=IBPhoenix |url=http://www.ibphoenix.com/main.nfs?a=ibphoenix&page=ibp_Mozilla0 |access-date=January 30, 2007 |archive-url=https://web.archive.org/web/20070914035447/http://www.ibphoenix.com/main.nfs?a=ibphoenix&page=ibp_Mozilla0 |archive-date=September 14, 2007}}</ref><ref>{{cite news |url=https://www.cnet.com/news/mozillas-firebird-gets-wings-clipped/ |title=Mozilla's Firebird gets wings clipped |last=Festa |first=Paul |date=May 7, 2003 |url-status=live |archive-url=https://web.archive.org/web/20180629063203/https://www.cnet.com/news/mozillas-firebird-gets-wings-clipped/ |archive-date=June 29, 2018 |publisher=[[CNET]] |access-date=January 30, 2007}}</ref> The Mozilla Foundation reassured them that the browser would always bear the name Mozilla Firebird to avoid confusion. After further pressure, Mozilla Firebird became Mozilla Firefox on February 9, 2004.<ref>{{cite news |url=https://www.cnet.com/news/mozilla-holds-fire-in-naming-fight/ |title=Mozilla holds 'fire' in naming fight |last=Festa |first=Paul |date=February 9, 2004 |url-status=live |archive-url=https://web.archive.org/web/20180629063422/https://www.cnet.com/news/mozilla-holds-fire-in-naming-fight/ |archive-date=June 29, 2018 |publisher=[[CNET]] |access-date=January 24, 2007}}</ref> The name Firefox was said to be derived from a nickname of the [[red panda]],<ref>{{cite web |title=Red panda |url=https://www.bbc.co.uk/nature/life/Red_Panda |archive-url=https://web.archive.org/web/20140111062619/http://www.bbc.co.uk/nature/life/Red_Panda |archive-date=January 11, 2014 |work=BBC Nature |access-date=August 20, 2014}}</ref> which became the mascot for the newly named project.<ref name="Firefox name FAQ">{{cite web |title=Firefox name FAQ |last1=Garrity |first1=Steven |last2=Markham |first2=Gervase |last3=Goodger |first3=Ben |last4=Decrem |first4=Bart |display-authors=etal |website=mozilla.org |url=https://www.mozilla.org/projects/firefox/firefox-name-faq.html |archive-url=https://web.archive.org/web/20120228204829/http://www.mozilla.org/projects/firefox/firefox-name-faq.html |archive-date=February 28, 2012 |access-date=March 13, 2012}}</ref> For the abbreviation of Firefox, Mozilla prefers ''Fx'' or ''fx,'' although it is often abbreviated as ''FF''<ref>{{cite web |title=Firefox 1.5 Release Notes |url=https://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/firefox/releases/1.5.html#FAQ |date=November 29, 2005 |website=mozilla.org archive |access-date=November 17, 2014 |archive-url=https://web.archive.org/web/20141118131918/http://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/firefox/releases/1.5.html#FAQ |archive-date=November 18, 2014 |url-status=live}}</ref> or Ff.

The Firefox project went through many versions before version 1.0 and had already gained a great deal of acclaim from numerous media outlets, such as ''[[Forbes]]''<ref>{{Cite web |url=https://www.forbes.com/2004/09/29/cx_ah_0929tentech.html |date=September 29, 2004 |url-access=subscription |title=Better Browser Now the Best |website=[[Forbes]] |access-date=May 20, 2020 |archive-date=May 3, 2019 |archive-url=https://web.archive.org/web/20190503084908/https://www.forbes.com/2004/09/29/cx_ah_0929tentech.html |url-status=live}}</ref> and ''[[The Wall Street Journal]]''.<ref>{{Cite web |url=http://ptech.wsj.com/archive/ptech-20040916.html |title=How to Protect Yourself From Vandals, Viruses If You Use Windows |first1=Walter S. |last1=Mossberg |website=Personal Technology from The Wall Street Journal |date=September 17, 2004 |archive-url=https://web.archive.org/web/20040917095122/http://ptech.wsj.com/archive/ptech-20040916.html |archive-date=September 17, 2004}}</ref> Among Firefox's popular features were the integrated [[pop-up blocker]], [[tabbed browsing]], and an extension mechanism for adding functionality. Although these features have already been available for some time in other browsers such as the [[Mozilla Suite]] and [[Opera (web browser)|Opera]], Firefox was the first of these browsers to have achieved large-scale adoption so quickly.<ref>{{Cite web |title=History of the Mozilla Project |url=https://www.mozilla.org/en-US/about/history/ |access-date=2024-12-03 |website=Mozilla}}</ref> Firefox attracted attention as an alternative to [[Internet Explorer]], which had come under fire for its alleged poor program design and insecurity—detractors cite IE's lack of support for certain Web standards, use of the potentially dangerous [[ActiveX]] component, and vulnerability to spyware and malware installation.{{Citation needed|date=September 2020}} Microsoft responded by releasing [[Windows XP]] Service Pack 2, which added several important security features to Internet Explorer 6.<ref>{{Cite web |last=Lake |first=Matt |title=Microsoft Windows XP SP2 review: Microsoft Windows XP SP2 |date=August 11, 2004 |url=https://www.cnet.com/reviews/microsoft-windows-xp-home-edition-w-sp2-review/ |access-date=September 20, 2021 |publisher=CNET |archive-date=February 11, 2021 |archive-url=https://web.archive.org/web/20210211204829/https://www.cnet.com/reviews/microsoft-windows-xp-home-edition-w-sp2-review/ |url-status=live}}</ref>

Version 1.0 of Firefox was released on November 9, 2004.<ref>{{Cite web |url=https://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/firefox/releases/1.0.html |title=Firefox 1.0 Release Notes |date=November 9, 2004 |website=mozilla.org archive |access-date=June 26, 2018 |archive-url=https://web.archive.org/web/20180627005158/https://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/firefox/releases/1.0.html |archive-date=June 27, 2018 |url-status=live}}</ref> This was followed by version 1.5 in November 2005, version 2.0 in October 2006, version 3.0 in June 2008, version 3.5 in June 2009, version 3.6 in January 2010, and version 4.0 in March 2011. From version 5 onwards, the development and release model changed into a "rapid" one; by the end of 2011 the stable release was version 9, and by the end of 2012 it reached version 17.<ref>{{Cite web |title=Mozilla Firefox Release Notes |url=https://www.mozilla.org/en-US/firefox/releases/ |access-date=September 20, 2021 |website=Mozilla |archive-date=September 17, 2021 |archive-url=https://web.archive.org/web/20210917224831/https://www.mozilla.org/en-US/firefox/releases/ |url-status=live}}</ref>

In 2016, Mozilla announced a project known as [[Quantum (Mozilla)|Quantum]], which sought to improve Firefox's Gecko engine and other components to improve the browser's performance, modernize its architecture, and transition the browser to a [[Process isolation|multi-process]] model. These improvements came in the wake of decreasing market share to [[Google Chrome]], as well as concerns that its performance was lagging in comparison. Despite its improvements, these changes required existing [[Add-on (Mozilla)|add-ons]] for Firefox to be made incompatible with newer versions, in favor of a new [[Browser extension|extension]] system that is designed to be similar to Chrome and other recent browsers. Firefox 57, which was released in November 2017, was the first version to contain enhancements from Quantum, and has thus been named ''Firefox Quantum''. A Mozilla executive stated that Quantum was the "biggest update" to the browser since version 1.0.<ref name="cnet57">{{cite news |url=https://www.cnet.com/special-reports/mozilla-firefox-fights-back-against-google-chrome/ |title=Inside Mozilla: Firefox fights back |last=Shankland |first=Stephen |date=August 4, 2017 |publisher=[[CNET]] |access-date=October 9, 2017 |archive-url=https://web.archive.org/web/20170803165258/https://www.cnet.com/special-reports/mozilla-firefox-fights-back-against-google-chrome/ |archive-date=August 3, 2017 |url-status=live}}</ref><ref>{{cite news |url=https://www.zdnet.com/article/why-you-should-root-for-mozillas-firefox-57-in-the-browser-wars/ |title=Why you should root for Mozilla's Firefox 57 in the browser wars |last=Dignan |first=Larry |date=August 6, 2017 |publisher=[[ZDNet]] |access-date=October 9, 2017 |archive-url=https://web.archive.org/web/20171211021103/https://www.zdnet.com/article/why-you-should-root-for-mozillas-firefox-57-in-the-browser-wars/ |archive-date=December 11, 2017 |url-status=live}}</ref><ref>{{Cite news |url=https://www.computerworld.com/article/3237054/internet/mozilla-seeks-return-to-glory-with-release-of-firefox-quantum.html |title=Mozilla seeks return to glory with release of Firefox Quantum |last=Keizer |first=Gregg |date=November 14, 2017 |work=[[Computerworld]] |access-date=December 11, 2017 |archive-url=https://web.archive.org/web/20171223114527/https://www.computerworld.com/article/3237054/internet/mozilla-seeks-return-to-glory-with-release-of-firefox-quantum.html |archive-date=December 23, 2017 |url-status=live |publisher=[[International Data Group]]}}</ref> Unresponsive and crashing pages only affect other pages loaded within the same process. While Chrome uses separate processes for each loaded tab, Firefox distributes tabs over four processes by default (since Quantum), to balance memory consumption and performance. The process count can be adjusted, where more processes increase performance at the cost of memory, therefore suitable for computers with larger RAM capacity.<ref>{{cite web |last1=Hoffman |first1=Chris |title=What's New in Firefox Quantum, the Firefox You've Been Waiting For |url=https://www.howtogeek.com/332449/whats-new-in-firefox-quantum/ |website=How-To Geek |access-date=October 29, 2021 |date=November 14, 2017 |archive-date=October 28, 2021 |archive-url=https://web.archive.org/web/20211028154320/https://www.howtogeek.com/332449/whats-new-in-firefox-quantum/ |url-status=live}}</ref><ref>{{cite web |title=Firefox's performance settings {{!}} Firefox Help |url=https://support.mozilla.org/en-US/kb/performance-settings |website=support.mozilla.org |access-date=October 29, 2021 |archive-date=October 29, 2021 |archive-url=https://web.archive.org/web/20211029162332/https://support.mozilla.org/en-US/kb/performance-settings |url-status=live}} (<code>about:config</code> property: <code>dom.ipc.processCount.web</code>)</ref>

On May 3, 2019, the expiry of an intermediate signing certificate on Mozilla servers caused Firefox to automatically disable and lock all browser extensions (add-ons).<ref name="FFAABlog">{{cite web |url=https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/ |title=Update Regarding Add-ons in Firefox |publisher=Mozilla |date=May 4, 2019 |access-date=May 4, 2019 |author=Needham, Kev |archive-url=https://web.archive.org/web/20190504142118/https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/ |archive-date=May 4, 2019 |url-status=live}}</ref><ref name="addon_expiry_brouhaha">{{cite news |last=Brinkmann |first=Martin |title=Your Firefox extensions are all disabled? That's a bug! |publisher=GHacks |date=May 4, 2019 |url=https://www.ghacks.net/2019/05/04/your-firefox-extensions-are-all-disabled-thats-a-bug/ |access-date=May 4, 2019 |archive-url=https://web.archive.org/web/20190504065552/https://www.ghacks.net/2019/05/04/your-firefox-extensions-are-all-disabled-thats-a-bug/ |archive-date=May 4, 2019 |url-status=live}}</ref> Mozilla began the roll-out of a fix shortly thereafter, using their Mozilla Studies component.<ref name="FFAABlog" /><ref name="addon_expiry_brouhaha" />

Support for [[Adobe Flash]] was dropped on January 6, 2021, with the release of Firefox 85.<ref>{{Cite web |title=End of support for Adobe Flash {{!}} Firefox Help |url=https://support.mozilla.org/en-US/kb/end-support-adobe-flash |access-date=January 2, 2024 |website=support.mozilla.org |archive-date=February 19, 2022 |archive-url=https://web.archive.org/web/20220219064257/https://support.mozilla.org/en-US/kb/end-support-adobe-flash |url-status=live }}</ref>

On June 1, 2021, Firefox's 'Proton' redesign was offered through its stable release channel<ref>{{Cite web |title=Firefox 89.0, See All New Features, Updates and Fixes |url=https://www.mozilla.org/en-US/firefox/89.0/releasenotes/ |access-date=2024-04-20 |website=Mozilla |archive-date=June 7, 2021 |archive-url=https://web.archive.org/web/20210607050657/https://www.mozilla.org/en-US/firefox/89.0/releasenotes/ |url-status=live }}</ref> after being made available in the beta builds.<ref>{{Cite web |title=Firefox Beta 89.0beta, See All New Features, Updates and Fixes |url=https://www.mozilla.org/en-US/firefox/89.0beta/releasenotes/ |access-date=2024-04-20 |website=Mozilla}}</ref> While users were initially allowed to revert to the old design through [[About URI scheme|about:config]], the corresponding [[Name–value pair|key-value pairs]] reportedly stopped working in later builds, resulting in criticism.<ref>{{Cite web |date=2021-07-14 |title=So. Now we can not even turn off proton? |url=https://discourse.mozilla.org/t/so-now-we-can-not-even-turn-off-proton/83108 |access-date=2024-04-20 |website=Mozilla Discourse |archive-date=April 20, 2024 |archive-url=https://web.archive.org/web/20240420103515/https://discourse.mozilla.org/t/so-now-we-can-not-even-turn-off-proton/83108 |url-status=live }}</ref> These included accessibility concerns<ref>{{Cite web |date=2022-06-03 |title=What's the status of post-Proton accessibility? |url=https://connect.mozilla.org/t5/discussions/what-s-the-status-of-post-proton-accessibility/m-p/7372#M3164 |access-date=2024-04-20 |website=connect.mozilla.org |archive-date=April 20, 2024 |archive-url=https://web.archive.org/web/20240420103518/https://connect.mozilla.org/t5/discussions/what-s-the-status-of-post-proton-accessibility/m-p/7372#M3164 |url-status=live }}</ref><ref>{{Cite web |date=2022-03-01 |title=Bring back menu icons |url=https://connect.mozilla.org/t5/ideas/bring-back-menu-icons/idi-p/46 |access-date=2024-04-20 |website=connect.mozilla.org}}</ref> despite Mozilla's claim to "continue to work with the accessibility community"<ref>{{Cite web |title=Can Firefox's new look save the web browser? |url=https://www.techradar.com/news/can-firefoxs-new-look-save-the-web-browser |first=Daryl|last=Baxter|date=6 June 2021 |website=TechRadar }}</ref> and had not been resolved {{As of|2024|10|lc=y}}.<ref>{{Cite web |title=1704131 – Hard to differentiate between active (foreground) and inactive (background) windows |url=https://bugzilla.mozilla.org/show_bug.cgi?id=1704131 |access-date=2024-10-27 |website=bugzilla.mozilla.org |archive-date=April 20, 2024 |archive-url=https://web.archive.org/web/20240420103515/https://bugzilla.mozilla.org/show_bug.cgi?id=1704131 |url-status=live }}</ref>

On January 13, 2022, an issue with Firefox's HTTP/3 implementation resulted in a widespread outage for several hours.<ref>{{cite web |url=https://9to5mac.com/2022/01/13/firefox-browser-suddenly-failing-to-load-websites-this-morning-heres-the-fix/ |title=Firefox is suddenly failing to load websites this morning, here's the fix |publisher=9To5Mac |date=January 13, 2021 |access-date=January 13, 2021 |archive-date=January 13, 2022 |archive-url=https://web.archive.org/web/20220113104452/https://9to5mac.com/2022/01/13/firefox-browser-suddenly-failing-to-load-websites-this-morning-heres-the-fix/amp/ |url-status=live }}</ref>

On September 26, 2023, Firefox 118.0 introduced on-device translation of web page content.<ref>{{cite web |url=https://www.mozilla.org/en-US/firefox/118.0/releasenotes/ |title=Firefox 118.0, See All New Features, Updates and Fixes |website=Mozilla |date=September 26, 2023 |access-date=February 29, 2024 |archive-date=November 8, 2023 |archive-url=https://web.archive.org/web/20231108034009/https://www.mozilla.org/en-US/firefox/118.0/releasenotes/ |url-status=live }}</ref>

On January 23, 2024, along with the release of Firefox 122.0, Mozilla introduced an official [[APT (software)#Sources|APT repository]] for [[Debian]]-based [[Linux distribution]]s.<ref>{{Cite web |url=https://www.mozilla.org/en-US/firefox/122.0/releasenotes/ |title=Firefox 122.0, See All New Features, Updates and Fixes |date=January 23, 2024 |access-date=January 27, 2024 |website=Mozilla |archive-url=https://web.archive.org/web/20240127213010/https://www.mozilla.org/en-US/firefox/122.0/releasenotes/ |archive-date=January 27, 2024 |url-status=live}}</ref>

== Features ==
{{main|List of Firefox features}}

Features of the desktop edition include [[tabbed browsing]], full-screen mode, [[spell checking]], [[incremental search]], [[smart bookmarks]], bookmarking and downloading through [[drag and drop]],<ref>{{cite web |title=Firefox Tip – Drag Bookmarks to your Toolbar |url=https://blog.mozilla.org/theden/2012/07/20/drag-bookmarks-to-your-toolbar/ |website=The Den |date=July 20, 2012 |publisher=Mozilla |access-date=October 29, 2021 |archive-date=October 29, 2021 |archive-url=https://web.archive.org/web/20211029162334/https://blog.mozilla.org/theden/2012/07/20/drag-bookmarks-to-your-toolbar/ |url-status=live}}</ref><ref>{{cite news |last1=Brinkmann |first1=Martin |title=Speed up the Download Process in Firefox with drag and drop? – gHacks Tech News |url=https://www.ghacks.net/2007/12/28/speed-up-download-process-in-firefox-with-drag-and-drop/ |website=gHacks Technology News |access-date=October 29, 2021 |date=December 28, 2007 |archive-date=October 29, 2021 |archive-url=https://web.archive.org/web/20211029162334/https://www.ghacks.net/2007/12/28/speed-up-download-process-in-firefox-with-drag-and-drop/ |url-status=live}}</ref> a [[download manager]], [[User profile#Digital User Profiles|user profile]] management,<ref>{{cite web |title=Profile Manager – Create, remove or switch Firefox profiles {{!}} Firefox Help |url=https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles |website=support.mozilla.org |access-date=October 29, 2021 |archive-date=October 29, 2021 |archive-url=https://web.archive.org/web/20211029160607/https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles |url-status=live}}</ref> [[private browsing]], bookmark tags, bookmark [[data export|exporting]],<ref>{{Cite web |url=https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer |title=Export Firefox bookmarks to an HTML file to back up or transfer bookmarks &#124; Firefox Help |website=support.mozilla.org |access-date=August 13, 2021 |archive-date=August 12, 2021 |archive-url=https://web.archive.org/web/20210812010516/https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer |url-status=live}}</ref> offline mode,<ref>{{cite web |last1=Kaufman |first1=Lori |title=How to Enable Offline Browsing in Firefox |url=https://www.howtogeek.com/263854/how-to-enable-offline-browsing-in-firefox/ |website=How-To Geek |access-date=August 31, 2021 |date=July 27, 2016 |archive-date=August 31, 2021 |archive-url=https://web.archive.org/web/20210831132207/https://www.howtogeek.com/263854/how-to-enable-offline-browsing-in-firefox/ |url-status=live}}</ref> a [[screenshot]] tool, [[web development tools]], a "page info" feature which shows a list of page metadata and multimedia items,<ref>{{Cite web |url=https://support.mozilla.org/en-US/kb/firefox-page-info-window |title=Firefox Page Info window – Firefox Help |access-date=September 24, 2021 |archive-date=September 24, 2021 |archive-url=https://web.archive.org/web/20210924004942/https://support.mozilla.org/en-US/kb/firefox-page-info-window |url-status=live}}</ref> a configuration menu at <code>about:config</code> for [[power user]]s, and location-aware browsing (also known as "[[geolocation]]") based on a Google service.<ref name=mozgeo>{{cite web |title=Location-Aware Browsing |url=https://www.mozilla.com/firefox/geolocation/ |access-date=July 5, 2009 |publisher=Mozilla Foundation |archive-date=February 15, 2023 |archive-url=https://web.archive.org/web/20230215185449/http://www.mozilla.com/firefox/geolocation/ |url-status=live }} (section "''What information is being sent, and to whom? (...)''")</ref> Firefox has an integrated search system which uses Google by default in most markets.<ref name="techcrunch-google">{{cite web |url=https://techcrunch.com/2017/11/14/mozilla-terminates-its-deal-with-yahoo-and-makes-google-the-default-in-firefox-again/ |title=Mozilla terminates its deal with Yahoo and makes Google the default in Firefox again |last1=Lardinois |first1=Frederic |date=November 14, 2017 |website=TechCrunch |access-date=November 14, 2017 |archive-url=https://web.archive.org/web/20171114211602/https://techcrunch.com/2017/11/14/mozilla-terminates-its-deal-with-yahoo-and-makes-google-the-default-in-firefox-again/ |archive-date=November 14, 2017 |url-status=live}}</ref><ref>{{cite news |url=https://www.thurrott.com/cloud/web-browsers/mozilla-firefox/258006/is-mozilla-firefox-getting-sketchy |title=Is Mozilla Firefox getting sketchy? |first=Paul |last=Thurrott |newspaper=Thurrott.com |date=October 9, 2021 |access-date=August 25, 2022 |archive-date=August 25, 2022 |archive-url=https://web.archive.org/web/20220825172403/https://www.thurrott.com/cloud/web-browsers/mozilla-firefox/258006/is-mozilla-firefox-getting-sketchy |url-status=live }}</ref> [[DNS over HTTPS]] is another feature whose default behaviour is determined geographically.<ref>{{cite web |url=https://www.theverge.com/2020/2/25/21152335/mozilla-firefox-dns-over-https-web-privacy-security-encryption |title=Firefox turns controversial encryption on by default in the US |first=Jon |last=Porter |publisher=The Verge |date=February 25, 2020 |access-date=August 25, 2022 |archive-date=August 25, 2022 |archive-url=https://web.archive.org/web/20220825175408/https://www.theverge.com/2020/2/25/21152335/mozilla-firefox-dns-over-https-web-privacy-security-encryption |url-status=live }}</ref>

Firefox provides an environment for web developers in which they can use built-in tools, such as the Error Console or the [[DOM Inspector]], and [[browser extension|extensions]], such as [[Firebug (software)|Firebug]] and more recently there has been an integration feature with [[Pocket (service)|Pocket]]. Firefox Hello was an implementation of [[WebRTC]], added in October 2014, which allows users of Firefox and other compatible systems to have a video call, with the extra feature of screen and file sharing by sending a link to each other. Firefox Hello was scheduled to be removed in September 2016.<ref>{{cite news |url=https://www.digitaltrends.com/computing/mozilla-firefox-hello-discontinue-september/ |title=Hang up the phone: Mozilla to pull the plug on Firefox Hello in September |last=Parrish |first=Kevin |date=August 5, 2016 |website=[[Digital Trends]] |archive-url=https://web.archive.org/web/20170115104933/https://www.digitaltrends.com/computing/mozilla-firefox-hello-discontinue-september/ |archive-date=January 15, 2017 |url-status=live}}</ref>

Former features include a [[File Transfer Protocol]] (FTP) client for browsing file servers, the ability to block images from individual domains (until version 72),<ref name=FF72>{{cite web |title=Firefox 72.0, See All New Features, Updates and Fixes |url=https://www.mozilla.org/en-US/firefox/72.0/releasenotes/ |website=Mozilla |access-date=October 20, 2021 |date=January 7, 2020 |quote=Support for blocking images from individual domains has been removed from Firefox, because of low usage and poor user experience. |archive-date=January 7, 2020 |archive-url=https://web.archive.org/web/20200107143038/https://www.mozilla.org/en-US/firefox/72.0/releasenotes/ |url-status=live}}</ref> a [[Features of Firefox#3D Page Inspector|3D page inspector]] (versions 11 to 46), tab grouping (until version 44), and the ability to add customized extra toolbars (until version 28).<ref>{{cite web |title=Firefox 45 Will Remove Tab Groups Today, Get This Add-on To Replace It |url=https://news.slashdot.org/story/16/03/08/1446243/firefox-45-will-remove-tab-groups-today-get-this-add-on-to-replace-it |website=news.slashdot.org |date=March 8, 2016 |access-date=August 12, 2021 |archive-date=August 12, 2021 |archive-url=https://web.archive.org/web/20210812010822/https://news.slashdot.org/story/16/03/08/1446243/firefox-45-will-remove-tab-groups-today-get-this-add-on-to-replace-it |url-status=live}}</ref><ref>{{cite web |title=How to Add Extra Bookmarks Toolbars in Firefox |url=https://www.guidingtech.com/3524/extra-bookmarks-toolbar-firefox/ |website=Guiding Tech |date=June 1, 2010 |access-date=August 12, 2021 |archive-date=August 12, 2021 |archive-url=https://web.archive.org/web/20210812010048/https://www.guidingtech.com/3524/extra-bookmarks-toolbar-firefox/ |url-status=live}}</ref><ref name=FF3D>{{cite web |title=3D view – Firefox Developer Tools {{!}} MDN |url=https://developer.mozilla.org/en-US/docs/Tools/3D_View |website=developer.mozilla.org |quote=From Firefox 47 onwards, 3D view is no longer available. |access-date=September 26, 2021 |archive-date=September 26, 2021 |archive-url=https://web.archive.org/web/20210926215611/https://developer.mozilla.org/en-US/docs/Tools/3D_View |url-status=live}}</ref>

=== Browser extensions ===
Functions can be added through [[add-on (Mozilla)|add-ons]] created by [[third-party developer]]s. Add-ons are primarily coded using an [[HTML]], [[CSS]], [[JavaScript]], with [[API]] known as [[WebExtensions]], which is designed to be compatible with [[Google Chrome]] and [[Microsoft Edge]] extension systems.<ref>{{Cite web |title=Browser Extensions |url=https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions |access-date=July 16, 2020 |website=MDN Web Docs |archive-date=July 19, 2020 |archive-url=https://web.archive.org/web/20200719033959/https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions |url-status=live}}</ref> Firefox previously supported add-ons using the [[XUL]] and [[XPCOM]] APIs, which allowed them to directly access and manipulate much of the browser's internal functionality. As compatibility was not included in the multi-process architecture, XUL add-ons have been deemed ''Legacy add-ons'' and are no longer supported on Firefox 57 "Quantum" and newer.<ref>{{Cite web |url=https://blog.mozilla.org/addons/2017/08/10/upcoming-changes-compatibility/ |title=Upcoming Changes in Compatibility Features |last=Villalobos |first=Jorge |date=August 10, 2017 |website=Mozilla Add-ons Blog |access-date=December 11, 2017 |archive-url=https://web.archive.org/web/20171226113447/https://blog.mozilla.org/addons/2017/08/10/upcoming-changes-compatibility/ |archive-date=December 26, 2017 |url-status=live}}</ref><ref>{{Cite news |url=https://arstechnica.com/information-technology/2015/08/mozilla-sets-plan-to-dump-firefox-add-ons-move-to-chrome-like-extensions/ |title=Mozilla sets plan to dump Firefox add-ons, move to Chrome-like extensions |last=Bright |first=Peter |date=August 21, 2015 |work=Ars Technica |access-date=December 11, 2017 |archive-url=https://web.archive.org/web/20171201203245/https://arstechnica.com/information-technology/2015/08/mozilla-sets-plan-to-dump-firefox-add-ons-move-to-chrome-like-extensions/ |archive-date=December 1, 2017 |url-status=live}}</ref>

Mozilla has occasionally installed extensions for users without their permission. This happened in 2017 when an extension designed to promote the show ''[[Mr. Robot]]'' was silently added in an update to Firefox.<ref>{{cite web |url=https://www.theverge.com/2017/12/16/16784628/mozilla-mr-robot-arg-plugin-firefox-looking-glass |title=Mozilla faces blowback after slipping Mr Robot plugin into Firefox |first=Russell |last=Brandom |publisher=The Verge |date=December 16, 2017 |access-date=August 25, 2022 |archive-date=August 25, 2022 |archive-url=https://web.archive.org/web/20220825145358/https://www.theverge.com/2017/12/16/16784628/mozilla-mr-robot-arg-plugin-firefox-looking-glass |url-status=live }}</ref><ref>{{cite news |url=https://www.theregister.com/2017/12/18/mozilla_mr_robot_firefox_promotion/ |title=Mozilla's creepy Mr Robot stunt in Firefox flops in touching tribute to TV show's 2nd season |first=Shaun |last=Nichols |work=The Register |date=December 18, 2017 |access-date=August 25, 2022 |archive-date=August 25, 2022 |archive-url=https://web.archive.org/web/20220825145031/https://www.theregister.com/2017/12/18/mozilla_mr_robot_firefox_promotion/ |url-status=live }}</ref>

=== Themes ===
Firefox can have themes added to it, which users can create or download from third parties to change the appearance of the browser.<ref name="ars-webextensions">{{cite web |title=Mozilla sets plan to dump Firefox add-ons, move to Chrome-like extensions |url=https://arstechnica.com/information-technology/2015/08/mozilla-sets-plan-to-dump-firefox-add-ons-move-to-chrome-like-extensions/ |website=Ars Technica |access-date=August 22, 2015 |date=August 21, 2015 |archive-url=https://web.archive.org/web/20150822085215/http://arstechnica.com/information-technology/2015/08/mozilla-sets-plan-to-dump-firefox-add-ons-move-to-chrome-like-extensions/ |archive-date=August 22, 2015 |url-status=live}}</ref><ref>{{cite web |title=Social & Communication: Add-ons for Firefox |url=https://addons.mozilla.org/en-US/firefox/extensions/social-communication/ |website=addons.mozilla.org |access-date=November 16, 2015 |archive-url=https://web.archive.org/web/20151203235652/https://addons.mozilla.org/en-US/firefox/extensions/social-communication/ |archive-date=December 3, 2015 |url-status=live}}</ref> Firefox also provides dark, light, and system themes.

=== Guest session ===
In 2013, Firefox for Android added a ''guest session'' mode, which wiped browsing data such as tabs, cookies, and history at the end of each guest session. Guest session data was kept even when restarting the browser or device, and deleted only upon a manual exit. The feature was removed in 2019, purportedly to "''streamline the experience''".<ref>{{cite web |title=Share Your Firefox with Friends & Family While Keeping Your Web Information Private with Guest Browsing |url=https://blog.mozilla.org/blog/2013/10/29/share-your-firefox-with-friends-family-while-keeping-your-web-information-private-with-guest-browsing |website=The Mozilla Blog |date=October 29, 2013 |access-date=January 27, 2021 |archive-date=January 27, 2021 |archive-url=https://web.archive.org/web/20210127033206/https://blog.mozilla.org/blog/2013/10/29/share-your-firefox-with-friends-family-while-keeping-your-web-information-private-with-guest-browsing/ |url-status=live}}</ref><ref>{{Cite web |url=https://support.mozilla.org/en-US/kb/share-your-android-device-firefox-guest-session |title=Share your Android device with a Firefox Guest Session &#124; Firefox for Android (ESR) Help |website=support.mozilla.org |access-date=January 27, 2021 |archive-date=January 27, 2021 |archive-url=https://web.archive.org/web/20210127031057/https://support.mozilla.org/en-US/kb/share-your-android-device-firefox-guest-session |url-status=live}}</ref>

=== Standards ===
[[File:Acid3 Mozilla Firefox test.png|thumb|The result of the [[Acid3]] test on Firefox 17]]

Firefox implements many [[web standards]], including [[HTML]], [[XML]], [[XHTML]], [[MathML]], [[SVG]] 1.1 (full),<ref>{{Cite web |title="SVG" {{!}} Can I use... Support tables for HTML5, CSS3, etc |url=https://caniuse.com/?search=SVG |access-date=December 13, 2021 |website=caniuse.com |archive-date=December 7, 2023 |archive-url=https://web.archive.org/web/20231207173656/https://caniuse.com/?search=SVG |url-status=live }}</ref> SVG 2 (partial),<ref>{{Cite web |url=https://developer.mozilla.org/en-US/docs/Web/SVG/SVG_2_support_in_Mozilla |title=SVG 2 support in Mozilla |website=MDN Web Docs |access-date=July 13, 2016 |archive-url=https://web.archive.org/web/20160920222508/https://developer.mozilla.org/en-US/docs/Web/SVG/SVG_2_support_in_Mozilla |archive-date=September 20, 2016 |url-status=live}}</ref><ref>{{cite web |url=https://developer.mozilla.org/en/SVG_in_Firefox |access-date=September 30, 2007 |title=SVG in Firefox |archive-url=https://web.archive.org/web/20080829121506/http://developer.mozilla.org/en/SVG_in_Firefox |archive-date=August 29, 2008 |url-status=live}}</ref> [[CSS]] (with extensions),<ref>{{cite web |url=https://developer.mozilla.org/en/CSS_Reference/Mozilla_Extensions |title=CSS Reference: Mozilla Extensions – MDC |publisher=Developer.mozilla.org |date=April 24, 2011 |access-date=August 17, 2011 |archive-url=https://web.archive.org/web/20110824232755/https://developer.mozilla.org/en/CSS_Reference/Mozilla_Extensions |archive-date=August 24, 2011 |url-status=live}}</ref> ECMAScript ([[JavaScript]]), [[Document Object Model|DOM]], [[XSLT]], [[XPath]], and [[APNG]] (Animated [[PNG]]) images with [[alpha transparency]].<ref>{{cite web |url=https://developer.mozilla.org/en/Gecko_FAQ |title=Which open standards is the Gecko development project working to support, and to what extent does it support them? |work=Gecko FAQ |access-date=January 24, 2007 |date=January 21, 2007 |publisher=Mozilla Developer Network |archive-url=https://web.archive.org/web/20080913104800/http://developer.mozilla.org/en/Gecko_FAQ |archive-date=September 13, 2008 |url-status=live}}</ref> Firefox also implements standards proposals created by the [[WHATWG]] such as client-side storage,<ref>{{cite web |url=http://www.whatwg.org/specs/web-apps/current-work/#storage |title=WHATWG specification&nbsp;– Web Applications 1.0&nbsp;– Working Draft. Client-side session and persistent storage |access-date=February 7, 2007 |date=February 7, 2007 |publisher=Web Hypertext Application Technology Working Group |archive-url=https://archive.today/20120801065328/http://www.whatwg.org/specs/web-apps/current-work/#storage |archive-date=August 1, 2012 |url-status=live}}</ref><ref>{{cite web |url=https://developer.mozilla.org/en/DOM/Storage |title=DOM:Storage |access-date=February 7, 2007 |date=September 30, 2007 |publisher=Mozilla Developer Network |archive-url=https://web.archive.org/web/20080901163339/http://developer.mozilla.org/en/DOM/Storage |archive-date=September 1, 2008 |url-status=live}}</ref> and the [[canvas element]].<ref>{{cite web |url=https://www.ibm.com/developerworks/xml/library/x-futhtml1/ |title=The future of HTML, Part 1: WHATWG |last=Dumbill |first=Edd |date=December 6, 2005 |publisher=[[IBM]] |access-date=January 24, 2007 |archive-url=https://web.archive.org/web/20071011142035/http://www.ibm.com/developerworks/xml/library/x-futhtml1/ |archive-date=October 11, 2007 |url-status=live}}</ref> These standards are implemented through the Gecko layout engine, and [[SpiderMonkey]] JavaScript engine. Firefox 4 was the first release to introduce significant HTML5 and CSS3 support.

Firefox has passed the [[Acid2]] standards-compliance test since version 3.0.<ref>{{cite web |url=http://www.betanews.com/article/Latest-Firefox-beta-passes-Acid2-test-IE8-claims-to-pass-also/1198178648 |title=Latest Firefox beta passes Acid2 test, IE8 claims to pass also |last=Fulton |first=Scott M. |date=December 20, 2007 |publisher=BetaNews |archive-url=https://web.archive.org/web/20180628072328/https://betanews.com/2007/12/20/latest-firefox-beta-passes-acid2-test-ie8-claims-to-pass-also/ |archive-date=June 28, 2018 |url-status=live |access-date=December 21, 2007}}</ref> Mozilla had originally stated that they did not intend for Firefox to pass the [[Acid3]] test fully because they believed that the SVG fonts part of the test had become outdated and irrelevant, due to [[WOFF]] being agreed upon as a standard by all major browser makers.<ref>{{cite web |url=http://www.conceivablytech.com/5430/products/why-firefox-4-will-never-pass-the-acid3-test/ |title=Why Firefox 4 Will Never Pass The Acid3 Test |last=Bailey |first=Daniel |archive-url=https://web.archive.org/web/20110203005137/http://www.conceivablytech.com/5430/products/why-firefox-4-will-never-pass-the-acid3-test/ |archive-date=February 3, 2011 |access-date=February 1, 2011}}</ref> Because the SVG font tests were removed from the Acid3 test in September 2011, Firefox 4 and greater scored 100/100.<ref>{{cite web |url=https://plus.google.com/107429617152575897589/posts/JdHnqpuUER4 |title=Acid3 2011 Update |last=Hickson |first=Ian |date=September 17, 2011 |access-date=September 17, 2011 |archive-url=https://web.archive.org/web/20111012170339/https://plus.google.com/107429617152575897589/posts/JdHnqpuUER4 |archive-date=October 12, 2011 |url-status=live}}</ref><ref>{{Cite web |url=https://www.tomsguide.com/us/acid3-browser-test-web-standard-compatibility-IE9,news-12583.html |title=Acid3 Test Simplified; All Modern Browsers Score 100 |last=Perry |first=Douglas |date=September 20, 2011 |website=Tom's Guide |publisher=Purch Group |access-date=July 6, 2018 |archive-url=https://web.archive.org/web/20180628015834/https://www.tomsguide.com/us/acid3-browser-test-web-standard-compatibility-IE9,news-12583.html |archive-date=June 28, 2018 |url-status=live}}</ref>

Firefox also implements "Safe Browsing,"<ref name=mozcomphishff3>{{cite web |title=Phishing and Malware Protection |url=https://www.mozilla.com/firefox/phishing-protection/ |access-date=November 29, 2009 |publisher=Mozilla Corp. |at=How does Phishing and Malware Protection work in Firefox? |archive-date=August 13, 2021 |archive-url=https://web.archive.org/web/20210813112436/https://support.mozilla.org/en-US/kb/how-does-phishing-and-malware-protection-work |url-status=live}}</ref> a [[proprietary format|proprietary protocol]]<ref name=googsb2prot>{{cite web |title=Client specification for the Google Safe Browsing v2.1 protocol |url=https://code.google.com/p/google-safe-browsing/wiki/Protocolv2Spec |access-date=November 29, 2009 |publisher=Google Inc. |quote=Do not use this protocol without explicit written permission from Google. '''Note''': This is not a license to use the defined protocol. [...] |archive-url=https://web.archive.org/web/20100211021242/http://code.google.com/p/google-safe-browsing/wiki/Protocolv2Spec |archive-date=February 11, 2010 |url-status=live}}</ref> from Google used to exchange data related to phishing and malware protection.

Firefox supports the playback of video content protected by [[HTML5]] [[Encrypted Media Extensions]] (EME), since version 38<!-- on Vista-->. For security and privacy reasons, EME is implemented within a wrapper of open-source code that allows execution of a [[proprietary software|proprietary]] [[digital rights management|DRM]] module by [[Adobe Systems]]—Adobe Primetime Content Decryption Module (CDM). CDM runs within a "[[sandbox (computer security)|sandbox]]" environment to limit its access to the system and provide it a randomized device ID to prevent services from [[Device fingerprint|uniquely identifying the device]] for tracking purposes. The DRM module, once it has been downloaded, is enabled and disabled in the same manner as other [[Plug-in (computing)|plug-ins]]. Since version 47,<ref>{{Cite web |url=https://www.mozilla.org/en-US/firefox/47.0/releasenotes/ |title=Firefox 47.0, See All New Features, Updates and Fixes |website=Mozilla |access-date=July 13, 2016 |archive-url=https://web.archive.org/web/20160719121556/https://www.mozilla.org/en-US/firefox/47.0/releasenotes/ |archive-date=July 19, 2016 |url-status=live}}</ref> "Google's Widevine CDM on Windows and Mac OS X so streaming services like [[Amazon Video]] can switch from [[Silverlight]] to encrypted HTML5 video" is also supported. Mozilla justified its partnership with Adobe and Google by stating:

{{blockquote|Firefox downloads and enables the Adobe Primetime and Google Widevine CDMs by default to give users a smooth experience on sites that require DRM. Each CDM runs in a separate container called a sandbox, and you will be notified when a CDM is in use. You can also disable each CDM and opt out of future updates|source=Watch DRM content on Firefox<ref>{{Cite web |url=https://support.mozilla.org/en-US/kb/enable-drm |title=Watch DRM content on Firefox &#124; Firefox Help |website=support.mozilla.org |access-date=July 13, 2016 |archive-url=https://web.archive.org/web/20150907004404/https://support.mozilla.org/en-US/kb/enable-drm |archive-date=September 7, 2015 |url-status=live}}</ref>}}

and that it is "an important step on Mozilla's roadmap to remove [[NPAPI]] plugin support."<!--The Widevine CDM runs in an open-source CDM sandbox in Firefox, providing better user security than NPAPI plugins.--><ref>{{cite web |url=https://blog.mozilla.org/futurereleases/2016/04/08/mozilla-to-test-widevine-cdm-in-firefox-nightly/ |title=Mozilla To Test Widevine CDM in Firefox Nightly |date=April 8, 2016 |access-date=July 13, 2016 |archive-url=https://web.archive.org/web/20160607175843/https://blog.mozilla.org/futurereleases/2016/04/08/mozilla-to-test-widevine-cdm-in-firefox-nightly/ |archive-date=June 7, 2016 |url-status=live}}</ref> Upon the introduction of EME support, builds of Firefox on Windows were also introduced that exclude support for EME.<ref>{{cite web |url=https://www.pcworld.com/article/2155440/firefox-will-get-drm-copy-protection-despite-mozillas-concerns.html |title=Mozilla hates it, but streaming video DRM is coming to Firefox |last=Kirk |first=Jeremy |date=May 15, 2014 |work=PC World |access-date=July 6, 2018 |archive-url=https://web.archive.org/web/20180515132001/https://www.pcworld.com/article/2155440/firefox-will-get-drm-copy-protection-despite-mozillas-concerns.html |archive-date=May 15, 2018 |url-status=live}}</ref><ref name="pcw-f38drm">{{cite web |url=https://www.pcworld.com/article/2922116/firefox-38-arrives-with-contentious-closed-source-drm-integrated-by-default.html |title=Firefox 38 arrives with contentious closed-source DRM integrated by default |last=Paul |first=Ian |date=May 13, 2015 |website=PC World |access-date=August 12, 2015 |archive-url=https://web.archive.org/web/20150802081751/http://www.pcworld.com/article/2922116/firefox-38-arrives-with-contentious-closed-source-drm-integrated-by-default.html |archive-date=August 2, 2015 |url-status=live}}</ref> The [[Free Software Foundation]] and [[Cory Doctorow]] condemned Mozilla's decision to support EME.<ref>{{cite web |url=https://www.infoq.com/news/2014/05/firefox-drm |title=Mixed reactions greet Mozilla plans to add HTML5 DRM in Firefox |first=James |last=Chesters |publisher=InfoQ |date=May 20, 2014 |access-date=May 6, 2019 |archive-url=https://web.archive.org/web/20190507011817/https://www.infoq.com/news/2014/05/firefox-drm |archive-date=May 7, 2019 |url-status=live}}</ref>

== Security ==
{{See also|Browser security}}

From its inception, Firefox was positioned as a security-focused browser. At the time, [[Internet Explorer]], the dominant browser, was facing a security crisis. Multiple vulnerabilities had been found, and [[malware]] like [[Download.ject|Download.Ject]] could be installed simply by visiting a compromised website. The situation was so bad that the US Government issued a warning against using Internet Explorer.<ref>{{Cite news |last=Captain |first=Sean |date=11 August 2019 |title=Firefox at 15: its rise, fall, and privacy-first renaissance |url=https://www.fastcompany.com/90428050/firefox-at-15-its-rise-fall-and-privacy-first-renaissance |access-date=6 June 2024 |website=[[Fast Company]] |archive-date=May 7, 2020 |archive-url=https://web.archive.org/web/20200507110319/https://www.fastcompany.com/90428050/firefox-at-15-its-rise-fall-and-privacy-first-renaissance |url-status=live }}</ref> Firefox, being less integrated with the operating system, was considered a safer alternative since it was less likely to have issues that could completely compromise a computer. This led to a significant increase in Firefox's popularity during the early 2000s as a more secure alternative.<ref name="WSJHowTo2">{{cite news |last=Mossberg |first=Walter S. |date=September 16, 2004 |title=How to Protect Yourself From Vandals, Viruses If You Use Windows |url=http://ptech.wsj.com/archive/ptech-20040916.html |archive-url=https://web.archive.org/web/20070221061526/http://ptech.wsj.com/archive/ptech-20040916.html |archive-date=February 21, 2007 |access-date=October 17, 2006 |work=The Wall Street Journal |quote=I suggest dumping Microsoft's Internet Explorer Web browser, which has a history of security breaches. I recommend instead  Mozilla Firefox, which is free at mozilla.org. It's not only more secure but also more modern and advanced, with tabbed browsing, which allows multiple pages to be open on one screen, and a better pop-up ad blocker than the belated one Microsoft recently added to IE.}}</ref><ref>{{cite news |last=Costa |first=Dan |date=March 24, 2005 |editor-last=Vamosi |editor-first=Scott |title=Mozilla Firefox – Review |url=https://reviews.cnet.com/browsers/mozilla-firefox/4505-3514_7-31117280.html |archive-url=https://web.archive.org/web/20071226062127/http://reviews.cnet.com/browsers/mozilla-firefox/4505-3514_7-31117280.html |archive-date=December 26, 2007 |publisher=[[CNET]]}}</ref> Moreover, Firefox was considered to have fewer actively exploitable [[security vulnerabilities]] compared to its competitors. In 2006, ''[[The Washington Post]]'' reported that exploit code for known security vulnerabilities in Internet Explorer was available for 284 days compared to only nine days for Firefox before the problem was fixed.<ref>{{cite news |last=Krebs |first=Brian |date=January 4, 2007 |title=Internet Explorer Unsafe for 284 Days in 2006 |url=http://blog.washingtonpost.com/securityfix/2007/01/internet_explorer_unsafe_for_2.html |url-status=live |archive-url=https://web.archive.org/web/20110424031839/http://blog.washingtonpost.com/securityfix/2007/01/internet_explorer_unsafe_for_2.html |archive-date=April 24, 2011 |access-date=January 24, 2007 |newspaper=The Washington Post}}</ref> A [[NortonLifeLock|Symantec]] study around the same period showed that even though Firefox had a higher number of vulnerabilities, on average vulnerabilities were fixed faster in Firefox than in other browsers during that period.<ref>{{cite news |last=Keizer |first=Gregg |date=September 25, 2006 |title=Firefox Sports More Bugs, But IE Takes 9 Times Longer To Patch |url=http://www.techweb.com/wire/security/193005335 |archive-url=https://web.archive.org/web/20080207192416/http://www.techweb.com/wire/security/193005335 |archive-date=February 7, 2008 |access-date=January 24, 2007 |publisher=TechWeb}}</ref>

During this period, Firefox used a [[Monolithic system|monolithic architecture]], like most browsers at the time. This meant all browser components ran in a single [[Process (computing)|process]] with access to all [[system resource]]s. This setup had multiple security issues. If a web page used too many resources, the entire Firefox process would hang or crash, affecting all tabs. Additionally, any exploit could easily access system resources, including user files. Between 2008 and 2012, most browsers shifted to a multiprocess architecture, isolating high-risk processes like rendering, media, GPU, and networking.<ref>{{Cite web |title=The Security Architecture of the Chromium Browser |url=https://seclab.stanford.edu/websec/chromium/ |access-date=2024-06-06 |website=seclab.stanford.edu |archive-date=June 6, 2024 |archive-url=https://web.archive.org/web/20240606161407/https://seclab.stanford.edu/websec/chromium/ |url-status=live }}</ref> However, Firefox was slower to adopt this change. It wasn't until 2015 that Firefox started its Electrolysis (e10s) project to implement sandboxing across multiple components. This rewrite relied on [[Inter-process communication|interprocess communication]] using [[Chromium (web browser)|Chromium]]'s interprocess communication library and placed various components, including the rendering component, in its sandbox.<ref>{{Cite web |date=26 November 2020 |title=Technical Overview of Multiprocess Firefox |url=https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Multiprocess_Firefox/Technical_overview |url-status=dead |archive-url=https://web.archive.org/web/20201126184717/https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Multiprocess_Firefox/Technical_overview |archive-date=26 November 2020 |access-date=6 June 2024 |website=Mozilla Developer Network}}</ref> Firefox released this rewrite in to beta in August 2016, noting a 10–20% increase in memory usage, which was lower than Chrome's at the time.<ref name=":0">{{Cite web |last=Callahan |first=Dan |date=2016-04-11 |title=The 'Why' of Electrolysis |url=https://blog.mozilla.org/addons/2016/04/11/the-why-of-electrolysis |access-date=2024-06-06 |website=Mozilla Add-ons Community Blog |archive-date=June 6, 2024 |archive-url=https://web.archive.org/web/20240606161412/https://blog.mozilla.org/addons/2016/04/11/the-why-of-electrolysis/ |url-status=live }}</ref> However, the rewrite caused issues with their legacy extension API, which was not designed to work cross-process and required [[Shim (computing)|shim code]] to function correctly.<ref name=":0" /> After over a year in beta, the rewrite was enabled by default all users of Firefox in November 2017.<ref>{{Cite news |url=https://arstechnica.com/information-technology/2016/12/firefox-takes-the-next-step-towards-rolling-out-multi-process-to-everyone/ |title=Firefox takes the next step toward rolling out multi-process to everyone |last=Bright |first=Peter |date=December 21, 2016 |newspaper=Ars Technica |access-date=December 25, 2016 |archive-url=https://web.archive.org/web/20161224234423/http://arstechnica.com/information-technology/2016/12/firefox-takes-the-next-step-towards-rolling-out-multi-process-to-everyone/ |archive-date=December 24, 2016 |url-status=live}}</ref>

In 2012, Mozilla launched a new project called [[Servo (software)|Servo]] to write a completely new and experimental browser engine utilizing [[Memory safety|memory safe]] techniques written in [[Rust (programming language)|Rust]].<ref>{{Cite news |last=Anderson |first=Tim |title=Mozilla will emit 'first version' of Servo-based Rust browser in June |url=https://www.theregister.com/2016/03/15/mozilla_to_release_first_version_of_servobased_browser_in_june/ |access-date=2024-06-07 |website=www.theregister.com |archive-date=June 7, 2024 |archive-url=https://web.archive.org/web/20240607050912/https://www.theregister.com/2016/03/15/mozilla_to_release_first_version_of_servobased_browser_in_june/ |url-status=live }}</ref> In 2018, Mozilla opted to integrate parts of the Servo project into the [[Gecko (software)|Gecko engine]] in a project codenamed the Quantum project.<ref>{{Cite web |title=Fearless Concurrency in Firefox Quantum {{!}} Rust Blog |url=https://blog.rust-lang.org/2017/11/14/Fearless-Concurrency-In-Firefox-Quantum.html |access-date=2024-06-07 |website=blog.rust-lang.org |archive-date=June 7, 2024 |archive-url=https://web.archive.org/web/20240607050912/https://blog.rust-lang.org/2017/11/14/Fearless-Concurrency-In-Firefox-Quantum.html |url-status=live }}</ref> The project completely overhauled Firefox's page rendering code, resulting in performance and stability gains while also improving the security of existing components.<ref>{{Cite web |title=Entering the Quantum Era—How Firefox got fast again and where it's going to get faster |url=https://hacks.mozilla.org/2017/11/entering-the-quantum-era-how-firefox-got-fast-again-and-where-its-going-to-get-faster |access-date=2024-06-07 |website=Mozilla Hacks – the Web developer blog}}</ref> Additionally, the older incompatible extension API was removed in favour of a WebExtension API that more closely resembled Google Chrome's extension system. This broke compatibility with older extensions but resulted in fewer vulnerabilities and a much more maintainable extension system.<ref>{{Cite web |last=Ellis |first=Cat |date=2017-11-14 |title=Firefox Quantum is here, and it wants to win you back |url=https://www.techradar.com/news/firefox-quantum-is-here-and-it-wants-to-win-you-back |access-date=2024-06-07 |website=TechRadar}}</ref> While the Servo project was intended to replace more parts of the Gecko Engine,<ref>{{Cite web |title=Firefox will get overhaul in bid to get you interested again |url=https://www.cnet.com/tech/services-and-software/firefox-mozilla-gets-overhaul-in-a-bid-to-get-you-interested-again/ |access-date=2024-06-07 |website=CNET |archive-date=July 14, 2022 |archive-url=https://web.archive.org/web/20220714172029/https://www.cnet.com/tech/services-and-software/firefox-mozilla-gets-overhaul-in-a-bid-to-get-you-interested-again/ |url-status=live }}</ref> this plan never came to fruition. In 2020, Mozilla laid off all developers on the Servo team transferring ownership of the project to the [[Linux Foundation]].<ref>{{Cite news |last=Proven |first=Liam |title=Rusty revenant Servo returns to render once more |url=https://www.theregister.com/2023/09/27/servo_returns/ |access-date=7 June 2024 |website=www.theregister.com |archive-date=June 7, 2024 |archive-url=https://web.archive.org/web/20240607050912/https://www.theregister.com/2023/09/27/servo_returns/ |url-status=live }}</ref>

== Privacy ==
When Firefox was initially released, it used a custom script permission policy where scripts that were signed by the page could gain access to higher privilege actions, such as the ability to set a user's preferences. However, this model was not widely used and was later discontinued by Firefox. Modern day Firefox instead follows the standard [[same-origin policy]] permission model that is followed by most modern browsers which disallows scripts from accessing any privileged data including data about other websites.<ref>{{cite web |url=https://developer.mozilla.org/En/Same_origin_policy_for_JavaScript |title=The Same Origin Policy |date=June 8, 2001 |access-date=November 12, 2007 |publisher=Mozilla Developer Network |archive-url=https://web.archive.org/web/20081014022433/http://developer.mozilla.org/En/Same_origin_policy_for_JavaScript |archive-date=October 14, 2008 |url-status=live}}</ref>

It uses [[Transport Layer Security|TLS]] to protect communications with web servers using strong [[cryptography]] when using the [[HTTPS]] protocol.<ref>{{cite web |url=https://www.mozilla.org/projects/security/pki/psm/help_21/ssl_help.html |title=Privacy & Security Preferences&nbsp;– SSL |access-date=January 24, 2007 |date=August 31, 2001 |publisher=Mozilla |archive-url=https://web.archive.org/web/20070207074919/http://www.mozilla.org/projects/security/pki/psm/help_21/ssl_help.html |archive-date=February 7, 2007 |url-status=live}}</ref> The freely available [[HTTPS Everywhere]] add-on enforces HTTPS, even if a regular HTTP [[URL]] is entered; this feature is now part of the browser.<ref>{{Cite web |date=2025-02-18 |title=HTTPS-Only Mode in Firefox |url=https://support.mozilla.org/en-US/kb/https-only-prefs |website=Mozilla}}</ref> Firefox supports HTTP/2.<ref>{{Cite web |url=https://www.browsermentor.com/why-you-should-use-firefox/ |title=Why You Should Use Firefox: 7 Reasons – BrowserMentor |first=Rahul |last=B |date=February 26, 2021 |access-date=February 26, 2021 |archive-date=August 13, 2021 |archive-url=https://web.archive.org/web/20210813112455/https://www.browsermentor.com/why-you-should-use-firefox/ |url-status=live}}</ref>

In February 2013, plans were announced for Firefox 22 to disable [[third-party cookie]]s by default. However, the introduction of the feature was then delayed so Mozilla developers could "collect and analyze data on the effect of blocking some third-party cookies." Mozilla also collaborated with [[Stanford University]]'s "Cookie Clearinghouse" project to develop a [[blacklist]] and [[whitelist]] of sites that will be used in the filter.<ref name="pcmag-tpcookies">{{cite news |url=https://www.pcmag.com/article2/0,2817,2415810,00.asp |title=Firefox 22 to Disable Third-Party Cookies by Default |last=Murphy |first=David |date=February 24, 2013 |work=PC Magazine |access-date=September 21, 2013 |archive-url=https://web.archive.org/web/20130926022552/http://www.pcmag.com/article2/0,2817,2415810,00.asp |archive-date=September 26, 2013 |url-status=live}}</ref><ref name="cw-cookieblocking">{{cite news |url=http://www.computerworld.com/s/article/9240218/Mozilla_again_postpones_Firefox_third_party_cookie_blocking_this_time_for_months |title=Mozilla again postpones Firefox third-party cookie-blocking, this time for months |last=Keizer |first=Gregg |date=June 20, 2013 |work=Computerworld |access-date=September 21, 2013 |archive-url=https://web.archive.org/web/20130926102706/http://www.computerworld.com/s/article/9240218/Mozilla_again_postpones_Firefox_third_party_cookie_blocking_this_time_for_months |archive-date=September 26, 2013 |url-status=live}}</ref>

Version 23, released in August 2013, followed the lead of its competitors by blocking [[HTML element#Frames|iframe]], stylesheet, and script resources served from non-HTTPS servers embedded on HTTPS pages by default. Additionally, [[JavaScript]] could also no longer be disabled through Firefox's preferences, and JavaScript was automatically re-enabled for users who upgraded to 23 or higher with it disabled. The change was made because JavaScript was being used across a majority of websites on the web, and disabling JavaScript could potentially have untoward repercussions on inexperienced users who are unaware of its impact. Firefox also cited the fact that extensions like [[NoScript]], which can disable JavaScript in a more controlled fashion, were widely available. The following release added the ability to disable JavaScript through the developer tools for testing purposes.<ref name="ff23-relnotes">{{cite web |url=https://www.mozilla.org/en-US/firefox/23.0/releasenotes/ |title=Firefox 23 Release Notes |date=August 6, 2013 |publisher=[[Mozilla.org]] |access-date=March 14, 2014 |archive-url=https://web.archive.org/web/20140328214014/http://www.mozilla.org/en-US/firefox/23.0/releasenotes/ |archive-date=March 28, 2014 |url-status=live}}</ref><ref>{{cite news |url=https://arstechnica.com/information-technology/2013/08/firefox-23-lands-with-a-new-logo-and-mixed-content-blocking/ |title=Firefox 23 lands with a new logo and mixed content blocking |last=Bright |first=Peter |date=August 6, 2013 |work=[[Ars Technica]] |access-date=March 14, 2014 |archive-url=https://web.archive.org/web/20140218022903/http://arstechnica.com/information-technology/2013/08/firefox-23-lands-with-a-new-logo-and-mixed-content-blocking/ |archive-date=February 18, 2014 |url-status=live}}</ref><ref>{{cite news |url=http://www.extremetech.com/computing/163291-firefox-23-finally-kills-the-blink-tag-removes-ability-to-turn-off-javascript-introduces-new-logo |title=Firefox 23 finally kills the blink tag, removes ability to turn off JavaScript, introduces new logo |last=Anthony |first=Sebastian |date=August 7, 2013 |newspaper=ExtremeTech |access-date=March 14, 2014 |archive-url=https://web.archive.org/web/20140329071544/http://www.extremetech.com/computing/163291-firefox-23-finally-kills-the-blink-tag-removes-ability-to-turn-off-javascript-introduces-new-logo |archive-date=March 29, 2014 |url-status=live}}</ref>

Beginning with Firefox 48, all extensions must be signed by Mozilla to be used in release and beta versions of Firefox. Firefox 43 blocked unsigned extensions but allowed enforcement of extension signing to be disabled. All extensions must be submitted to [[Mozilla Add-ons]] and be subject to code analysis to be signed, although extensions do not have to be listed on the service to be signed.<ref>{{cite web |title=Addons/Extension Signing |url=https://wiki.mozilla.org/Addons/Extension_Signing |website=Mozilla wiki |access-date=November 23, 2019 |archive-url=https://web.archive.org/web/20191010005008/https://wiki.mozilla.org/Addons/Extension_Signing |archive-date=October 10, 2019 |url-status=live}}</ref><ref name="signing">{{cite web |url=https://blog.mozilla.org/addons/2015/02/10/extension-signing-safer-experience/ |title=Introducing Extension Signing: A Safer Add-on Experience |last1=Villalobos |first1=Jorge |date=February 10, 2015 |website=Mozilla Add-ons Blog |access-date=November 23, 2019 |archive-url=https://web.archive.org/web/20191029202549/https://blog.mozilla.org/addons/2015/02/10/extension-signing-safer-experience/ |archive-date=October 29, 2019 |url-status=live}}</ref> On May 2, 2019, Mozilla announced that it would be strengthening the signature enforcement with methods that included the retroactive disabling of old extensions now deemed to be insecure.<ref>{{cite web |url=https://gizmodo.com/firefox-fixes-borked-extensions-for-everyone-but-legacy-1834548155 |title=Firefox fixes borked extensions for everyone but legacy users |first=Victoria |last=Song |publisher=Gizmodo |date=May 6, 2019 |access-date=May 6, 2019 |archive-url=https://web.archive.org/web/20190506165014/https://gizmodo.com/firefox-fixes-borked-extensions-for-everyone-but-legacy-1834548155 |archive-date=May 6, 2019 |url-status=live}}</ref>
<!-- In Firefox versions before 7.0, an [[information bar]] appears on the browser's first start asking users whether they would like to send performance statistics, or "telemetry", to [[Mozilla Corporation|Mozilla]]. This telemetry exists as of May 2024{{Cn|date=June 2024}} and is enabled by default in development versions of Firefox, but not in release versions.<ref>{{cite web |url=https://wiki.mozilla.org/Telemetry/FAQ#Why_is_Telemetry_enabled_by_default_on_the_Firefox_pre-release_channels.3F |title=FAQ – Why is Telemetry enabled by default on the Firefox pre-release channels? |website=MozillaWiki |publisher=Mozilla |access-date=July 26, 2014 |archive-url=https://web.archive.org/web/20140810084936/https://wiki.mozilla.org/Telemetry/FAQ#Why_is_Telemetry_enabled_by_default_on_the_Firefox_pre-release_channels.3F |archive-date=August 10, 2014 |url-status=live}}</ref> According to Mozilla's privacy policy,<ref>{{cite web |url=https://www.mozilla.org/en-US/privacy/firefox/ |title=Mozilla Firefox Privacy Policy |publisher=[[Mozilla Corporation]], a subsidiary of the [[Mozilla Foundation]] |access-date=June 18, 2018 |archive-url=https://web.archive.org/web/20180614123101/https://www.mozilla.org/en-US/privacy/firefox/ |archive-date=June 14, 2018 |url-status=live}}</ref> these statistics are stored only in aggregate format, and the only [[personally identifiable information]] transmitted is the user's [[IP address]]. -->

Since version 60 Firefox includes the option to use [[DNS over HTTPS]] (DoH), which causes [[Domain Name System|DNS lookup]] requests to be sent encrypted over the HTTPS protocol.<ref>{{cite journal |url=https://heise.de/-4079547 |title=Private Auskunft – DNS mit Privacy und Security vor dem Durchbruch |journal=C't |date=June 22, 2018 |volume=2018 |issue=14 |pages=176–179 |access-date=July 25, 2018 |language=de |archive-date=November 12, 2020 |archive-url=https://web.archive.org/web/20201112151338/https://www.heise.de/select/ct/2018/14/1530492966691096 |url-status=live}}</ref><ref>{{cite journal |url=https://www-heise-de.translate.goog/select/ct/2018/14/1530492966691096?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB&_x_tr_pto=nui |title=About Encrypted DNS by Carsten Strotmann & Jürgen Schmidt |journal=C't |date=June 22, 2018 |volume=2018 |issue=14 |pages=176–179 |access-date=July 25, 2018 |language=de |archive-date=November 12, 2020 |archive-url=https://web.archive.org/web/20201112151338/https://www.heise.de/select/ct/2018/14/1530492966691096 |url-status=live |quote=This is the English Translation of Previous Citation.}}</ref> To use this feature the user must set certain preferences beginning with "network.trr" (Trusted Recursive Resolver) in [[about:config]]: if network.trr.mode is 0, DoH is disabled; 1 activates DoH in addition to unencrypted DNS; 2 causes DoH to be used before unencrypted DNS; to use only DoH, the value must be 3. By setting network.trr.uri to the URL, special [[Cloudflare]] servers will be activated. Mozilla has a privacy agreement with this server host that restricts its collection of information about incoming DNS requests.<ref>{{cite web |url=https://developers.cloudflare.com/1.1.1.1/commitment-to-privacy/privacy-policy/firefox/ |title=Cloudflare Resolver for Firefox |website=cloudflare.com |access-date=July 25, 2018 |archive-url=https://web.archive.org/web/20180722071110/https://developers.cloudflare.com/1.1.1.1/commitment-to-privacy/privacy-policy/firefox/ |archive-date=July 22, 2018 |url-status=dead}}</ref>

On May 21, 2019, Firefox was updated to include the ability to block scripts that used a computer's [[CPU]] to mine [[cryptocurrency]] without a user's permission, in Firefox version 67.0. The update also allowed users to block known [[Device fingerprint|fingerprinting]] scripts that track their activity across the web, however it does not resist fingerprinting on its own.<ref>{{cite web |last1=Wood |first1=Marissa |title=Latest Firefox Release is Faster than Ever |url=https://blog.mozilla.org/blog/2019/05/21/latest-firefox-release-is-faster-than-ever/ |website=The Mozilla Blog |access-date=May 22, 2019 |archive-url=https://web.archive.org/web/20190521231343/https://blog.mozilla.org/blog/2019/05/21/latest-firefox-release-is-faster-than-ever/ |archive-date=May 21, 2019 |url-status=live}}</ref> In February 2021, Firefox launched Total Cookie Protection in version 86 to offer protection against [[cross-site tracking]], without breaking the websites users visit.<ref>{{cite web |date=March 25, 2021 |title=Firefox 86 Introduces Total Cookie Protection |url=https://blog.mozilla.org/security/2021/02/23/total-cookie-protection/ |access-date=September 23, 2025 |website=Mozilla Security Blog |archive-date=September 4, 2025 |archive-url=https://web.archive.org/web/20250904052611/https://blog.mozilla.org/security/2021/02/23/total-cookie-protection/ |url-status=live}}</ref> Also known as state partitioning, Total Cookie Protection works by creating a separate "cookie jar" for each website, thereby preventing data from being shared between websites. The feature, which was named one of 2021's best security innovations by [[Popular Science]],<ref>{{cite web |url=https://www.popsci.com/technology/best-of-whats-new-2021/#h-grand-award-winner-5 |title=The 100 greatest innovations of 2021 |website=Popular Science |date=Dec 1, 2021 |access-date=September 23, 2025 }}</ref> also isolates local storage, service workers, and other common ways for sites to store data.<ref>{{cite web |url=https://hacks.mozilla.org/2021/02/introducing-state-partitioning/ |title=Introducing State Partitioning
 |website=Mozilla Hacks |date=February 23, 2021 |access-date=September 23, 2025 }}</ref> Total Cookie Protection was enabled by default in 2022.<ref>{{cite web |url=https://blog.mozilla.org/en/mozilla/firefox-rolls-out-total-cookie-protection-by-default-to-all-users-worldwide/ |title=Firefox Rolls out Total Cookie Protection by Default to All Users Worldwide |website=Distilled, Mozilla Blog |date=June 14, 2022 |access-date=September 23, 2025 |url-status=bot: unknown |archive-date=October 20, 2022 |archive-url=https://web.archive.org/web/20221020015500/https://blog.mozilla.org/en/mozilla/firefox-rolls-out-total-cookie-protection-by-default-to-all-users-worldwide/ }}</ref>

== Localizations ==
Firefox is a widely [[Internationalization and localization|localized]] web browser. Mozilla uses the in-house Pontoon localization platform.<ref>{{cite web |url=https://archive.fosdem.org/2023/schedule/event/mozilla_localize_your_project_with_pontoon/ |title=Localize your open source project with Pontoon |website=Fosdem |access-date=March 26, 2024}}</ref> The first official release in November 2004 was available in 24 different languages and for 28 [[Locale (computer software)|locales]].<ref>{{cite web |url=https://archive.mozilla.org/pub/mozilla.org/firefox/releases/1.0/win32/ |title=Index of /pub/firefox/releases/1.0/win32/ |access-date=August 22, 2011 |archive-url=https://web.archive.org/web/20221202050508/https://archive.mozilla.org/pub/mozilla.org/firefox/releases/1.0/win32/ |archive-date=December 2, 2022 |url-status=live}}</ref> In 2019, Mozilla released Project Fluent a localization system that allows translators to be more flexible with their translation than to be constrained in one-to-one translation of strings.<ref>{{Cite web |url=https://projectfluent.org/ |title=Project Fluent |website=Project Fluent |access-date=March 26, 2024 |archive-url=https://web.archive.org/web/20240326094057/https://projectfluent.org/ |archive-date=March 26, 2024 |url-status=live}}</ref><ref>{{cite web |date=2019-04-17 |url=https://blog.mozilla.org/press/2019/04/mozilla-launches-fluent-1-0-to-revolutionize-software-localization |title=Mozilla launches Fluent 1.0 to revolutionize software localization |website=Mozilla Press Center |access-date=March 26, 2024 |archive-url=https://web.archive.org/web/20240326094308/https://blog.mozilla.org/press/2019/04/mozilla-launches-fluent-1-0-to-revolutionize-software-localization/ |archive-date=March 26, 2024 |url-status=live}}</ref> {{As of|2025|12|post=,}} the supported versions of Firefox are available in 97 locales (88 languages).<ref name="languages">{{cite web |url=https://archive.mozilla.org/pub/firefox/releases/ |title=Mozilla Firefox release files |publisher=Mozilla |access-date=October 1, 2020 |archive-url=https://web.archive.org/web/20191009133701/https://archive.mozilla.org/pub/firefox/releases/ |archive-date=October 9, 2019 |url-status=live}}</ref>

== Platform availability ==
There are desktop versions of Firefox for Microsoft Windows, macOS, and Linux, while [[Firefox for Android]] is available for Android (formerly Firefox for mobile, it also ran on [[Maemo]], [[MeeGo]], and [[Firefox OS]]) and [[Firefox for iOS]] is available for iOS. Smartphones that [[Linux for mobile devices|support Linux]] but not Android, or iOS apps can also run Firefox in its desktop version, for example using [[postmarketOS]], [[Mobian]] or [[Ubuntu Touch]].<ref>{{cite web|url=https://ignne.github.io/firefox-in-ubuntu-touch-libertine.html|title=Firefox in Ubuntu Touch (Libertine)}}</ref>

{{Firefox release compatibility}}

Firefox source code may be [[compiled]] for various operating systems; however, officially distributed binaries are provided for the following:

{| class="wikitable sortable" style="text-align: center;"
|+ Required hardware and software<ref name="sysreq 116.0">{{cite web |date=August 1, 2023 |title=Firefox System Requirements |url=https://www.mozilla.org/en-US/firefox/116.0/system-requirements/ |access-date=August 2, 2023 |website=mozilla.org |publisher=Mozilla Foundation |archive-date=August 1, 2023 |archive-url=https://web.archive.org/web/20230801182539/https://www.mozilla.org/en-US/firefox/116.0/system-requirements/ |url-status=live }}</ref>
|-
! Requirement
! Microsoft Windows
! Linux <small>desktop</small>
! macOS
! Android<ref name="mobile_req">{{cite web |title=Will Firefox work on my mobile device? |work=Mozlla Support |url=https://support.mozilla.org/en-US/kb/will-firefox-work-my-mobile-device |publisher=Mozilla |access-date=December 3, 2013 |archive-url=https://web.archive.org/web/20131202141442/https://support.mozilla.org/en-US/kb/will-firefox-work-my-mobile-device |archive-date=December 2, 2013 |url-status=live}}</ref>
! iOS
|-
! [[CPU]]
| colspan="2" | {{ubl
  |1&nbsp;GHz or faster compatible processor<ref name="ARMv7_and_8" /> ([[ARMv8-A|ARM64]] for the default release is supported on Windows but only for the Nightly release on Linux unless an ARM64 package from the Linux distribution is used<ref>{{Cite web |url=https://blog.mozilla.org/futurereleases/2019/04/11/firefox-beta-for-windows-10-on-qualcomm-snapdragon-always-connected-pcs-now-available |title=Firefox Beta for Windows 10 on Qualcomm Snapdragon Always Connected PCs Now Available |last=Harmston |first=Chuck |website=Future Releases |date=April 11, 2019 |access-date=April 4, 2020 |archive-date=February 21, 2020 |archive-url=https://web.archive.org/web/20200221193106/https://blog.mozilla.org/futurereleases/2019/04/11/firefox-beta-for-windows-10-on-qualcomm-snapdragon-always-connected-pcs-now-available/ |url-status=live}}</ref><ref>{{cite web|url=https://www.phoronix.com/news/Mozilla-Firefox-ARM64-Nightly|title=Mozilla Finally Begins Offering Firefox ARM64 Linux Binaries}}</ref>)
  |ESR 115: [[Pentium 4]] or newer with [[SSE2]] (or ARM64 for Windows)
}}
| Any [[x86-64]] and ARM64 CPU<ref name="ARMv7_and_8" />
| [[ARMv7]], ARM64 and [[x64]]<ref name="ARMv7_and_8">{{Cite web |url=https://firefox-source-docs.mozilla.org/build/buildsystem/supported-configurations.html |title=Supported build targets |website=Firefox Source Docs documentation |access-date=January 14, 2021 |archive-date=January 16, 2021 |archive-url=https://web.archive.org/web/20210116103308/https://firefox-source-docs.mozilla.org/build/buildsystem/supported-configurations.html |url-status=live}}</ref>
| ARM64
|-
! [[Random-access memory|Memory (RAM)]]
| colspan="3" | {{ubl
  |1&nbsp;[[Gigabyte|GB]] for the 32-bit version and 2&nbsp;GB for the 64-bit version
  |ESR 115: 512&nbsp;[[Megabyte|MB]] for the 32-bit version and 2&nbsp;GB for the 64-bit version
}}
| 384&nbsp;MB
| 2GB
|-
! [[Data storage device]] free space
| colspan="3" | {{ubl
  |500&nbsp;MB
  |ESR 115: 200&nbsp;MB
}}
| 80&nbsp;MB
| ~128&nbsp;MB<ref name="ios_req"/>
|-
! Operating system
| {{ubl
  |[[Windows 10]] or later
  |[[Windows Server 2016]] or later<ref name="sysreq 116.0" />
  |ESR 115: [[Windows 7]], [[Server 2008 R2]], [[Windows 8|8]], [[Server 2012]], [[Windows 8.1|8.1]] and [[Windows Server 2012 R2|Server 2012 R2]]
}}
| style="line-height:1.1em;"|
; Minimum
* [[GTK]] 3.14 or newer<ref name="sysreq 116.0" />
* [[C++ Standard Library|libstdc++]] 4.8.1 or newer
* [[X.Org Server|X.Org]] 1.0 or newer
* [[glibc]] 2.17 or newer

; Recommended
* [[NetworkManager]] 0.7 or newer
* [[DBus]] 1.0 or newer
* [[GNOME]] 2.16 or newer
* [[PulseAudio]]
* [[X.Org Server|X.Org]] 1.7 or newer
* libxtst 1.2.3 or newer
| {{ubl
  |[[macOS Catalina]] or newer<ref name="sysreq 116.0" />
  |ESR 115: [[macOS Sierra]]–[[macOS Mojave]]
}}
| [[Android Oreo]] or newer<ref name="Firefox for Android upgrade FAQs" />
| [[iOS 15]] or later<ref name="ios_req">{{cite web |title=Firefox: Private, Safe Browser |work=App Store |url=https://apps.apple.com/us/app/firefox-private-safe-browser/id989804926 |publisher=Apple |access-date=November 24, 2023 |archive-url=https://web.archive.org/web/20170830073541/https://itunes.apple.com/us/app/apple-store/id989804926 |archive-date=August 30, 2017 |url-status=live}}</ref>
|}<!-- If this may seem confusing, then Android 2.2 and/or ARMv6 are no longer supported. See Talk. Confirmed there.-->

=== Microsoft Windows ===
[[File:Firefox 136.0.4 showing the English Wikipedia.PNG|thumb|Firefox 136 on [[Windows 10]]]]
Firefox 1.0 was released for [[Windows 95]], as well as [[Windows NT 4.0]] or later. Some users reported the 1.x builds were operable (but not installable) on [[Windows NT 3.51]].<ref>{{cite web |url=http://www.c-amie.co.uk/technical/mozilla-firefox-and-windows-nt-3-51/ |title=Mozilla Firefox and Windows NT 3.51 |last=Tilley |first=Chris |date=April 21, 2006 |website=C:Amie |access-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181226084426/http://www.c-amie.co.uk/technical/mozilla-firefox-and-windows-nt-3-51/ |archive-date=December 26, 2018 |url-status=live}}</ref>

The version 42.0 release includes the first [[x64]] build. It required [[Windows 7]] or [[Server 2008 R2]].<ref>{{cite web |url=https://blog.mozilla.org/futurereleases/2015/12/15/firefox-64-bit-for-windows-available/ |title=Firefox 64-bit Web Browser for Windows Now Available |last=Mayo |first=Mark |date=December 15, 2015 |work=Future Releases |publisher=[[Mozilla Foundation]] |via=blog.mozilla.org |access-date=December 14, 2017 |archive-url=https://web.archive.org/web/20171214183058/https://blog.mozilla.org/futurereleases/2015/12/15/firefox-64-bit-for-windows-available/ |archive-date=December 14, 2017 |url-status=live}}</ref> Starting from version 49.0, Firefox for Windows requires and uses the [[SSE2]] instruction set.

In September 2013, Mozilla released a [[Universal Windows Platform apps|Metro-style version]] of Firefox, optimized for [[touchscreen]] use, on the "Aurora" release channel. However, on March 14, 2014, Mozilla cancelled the project because of a lack of user adoption.<ref name="fx-metrocancelled">{{cite web |last=Nightingale |first=Johnathan |date=March 14, 2014 |title=Update on Metro |url=https://blog.mozilla.org/futurereleases/2014/03/14/metro/ |url-status=live |archive-url=https://web.archive.org/web/20170424075847/https://blog.mozilla.org/futurereleases/2014/03/14/metro/ |archive-date=April 24, 2017 |access-date=March 14, 2014 |work=Firefox Future Releases Blog}}</ref><ref name="mozandroid-devices">{{cite web |title=Mozilla Firefox Web Browser – Supported Android Devices |url=https://support.mozilla.org/en-US/kb/will-firefox-work-my-mobile-device |url-status=live |archive-url=https://web.archive.org/web/20130626194325/http://support.mozilla.org/en-US/kb/will-firefox-work-my-mobile-device |archive-date=June 26, 2013 |access-date=July 20, 2013 |publisher=Mozilla}}</ref><ref name="engadget-firefoxmetro">{{cite news |last=Lutz |first=Zachary |date=September 21, 2013 |title=Firefox for Windows 8 enters Aurora channel with touch and gesture support |work=Engadget |url=https://www.engadget.com/2013/09/21/firefox-for-windows-8-enters-aurora-channel/ |access-date=September 21, 2013 |archive-url=https://web.archive.org/web/20130924082341/http://www.engadget.com/2013/09/21/firefox-for-windows-8-enters-aurora-channel/ |archive-date=September 24, 2013 |url-status=live}}</ref>

In March 2017, Firefox 52 ESR, the last version of the browser for [[Windows XP]] and [[Windows Vista]], was released.<ref>{{Cite web |date=2017-03-07 |title=Final Firefox version with Windows XP, plugin support released today |url=https://arstechnica.com/information-technology/2017/03/final-firefox-version-with-windows-xp-plugin-support-released-today/ |website=[[Ars Technica]] |access-date=2024-07-15 |archive-url=https://web.archive.org/web/20240114122205/https://arstechnica.com/information-technology/2017/03/final-firefox-version-with-windows-xp-plugin-support-released-today/ |archive-date=2024-01-14 |url-status=live}}</ref> Support for Firefox 52 ESR ended in June 2018.<ref>{{Cite web |last=Tung |first=Liam |date=October 5, 2017 |title=Windows XP users: Your last supported refuge in Firefox ends in 2018, says Mozilla |url=https://www.zdnet.com/article/windows-xp-users-your-last-supported-refuge-in-firefox-ends-in-2018-says-mozilla/ |website=[[ZDNET]] |access-date=2024-07-15 |archive-url=https://web.archive.org/web/20171008125800/http://www.zdnet.com/article/windows-xp-users-your-last-supported-refuge-in-firefox-ends-in-2018-says-mozilla/ |archive-date=October 8, 2017 |url-status=live}}</ref>

Traditionally, installing the Windows version of Firefox entails visiting the Firefox website and downloading an installer package, depending on the desired localization and system architecture. In November 2021, Mozilla made Firefox available on [[Microsoft Store]]. The Store-distributed package does not interfere with the traditional installation.<ref>{{Cite web |last=Warren |first=Tom |date=November 9, 2021 |title=Mozilla's Firefox browser arrives in the Windows store |url=https://www.theverge.com/2021/11/9/22771845/mozilla-firefox-microsoft-store-windows-download |website=[[The Verge]] |access-date=December 13, 2021 |archive-url=https://web.archive.org/web/20211213125011/https://www.theverge.com/2021/11/9/22771845/mozilla-firefox-microsoft-store-windows-download |archive-date=December 13, 2021 |url-status=live}}</ref><ref>{{Cite magazine |last=Pegoraro |first=Rob |date=November 9, 2021 |title=Firefox Arrives in the Microsoft Store |url=https://www.pcmag.com/news/firefox-arrives-in-the-microsoft-store |magazine=[[PC Magazine]] |publisher=[[Ziff Davis]] |access-date=December 13, 2021 |archive-url=https://web.archive.org/web/20211213125012/https://www.pcmag.com/news/firefox-arrives-in-the-microsoft-store |archive-date=December 13, 2021 |url-status=live}}</ref>

The last version of Firefox for Windows 7 and 8 is Firefox 115 ESR, which was released in July 2023.<ref>{{Cite web|url=https://www.theregister.com/2023/07/05/firefox_115_browser_windows/|title=Firefox 115 browser breathes life into old operating systems|date=5 July 2023|access-date=15 July 2024|website=[[The Register]]|last=Proven|first=Liam|archive-date=July 13, 2024|archive-url=https://web.archive.org/web/20240713035453/https://www.theregister.com/2023/07/05/firefox_115_browser_windows/|url-status=live}}</ref> Its [[End-of-life product|end-of-life]] was initially planned to be in October 2024,<ref>{{Cite news |last=Proven |first=Liam |date=11 July 2024 |title=Firefox 128 bumps system requirements for old boxes |url=https://www.theregister.com/2024/07/11/firefox_128_new_esr/ |access-date=15 July 2024 |website=[[The Register]] |archive-date=July 13, 2024 |archive-url=https://web.archive.org/web/20240713233516/https://www.theregister.com/2024/07/11/firefox_128_new_esr/ |url-status=live }}</ref> however in July 2024, a Mozilla employee announced in a comment on Reddit that the company consider extending the support beyond the initial date, the duration of that extension being yet to be defined.{{citation needed|date=March 2025}} In September 2024, the extension was announced for an initial period of six months.<ref name=":2">{{Cite web |date=2025-02-07 |title=Firefox ESR schedule |url=https://whattrainisitnow.com/release/?version=esr |access-date=2025-02-18 |archive-url=https://web.archive.org/web/20250207110108/https://whattrainisitnow.com/release/?version=esr |archive-date=February 7, 2025 }}</ref> In the release calendar page, a note states that Mozilla will re-evaluate the situation in early 2025 to see if another extension will be needed or not and statute about 115 ESR end-of-life then.<ref>{{Cite web |title=Firefox ESR schedule |url=https://whattrainisitnow.com/release/?version=esr |website=Firefox ESR schedule |access-date=2024-09-20 |archive-url=https://web.archive.org/web/20241001134137/https://whattrainisitnow.com/release/?version=esr |archive-date=2024-10-01 |url-status=live}}</ref> This extension has been renewed two more times, on February 18, 2025, and on September 3, 2025, for six additional months each time, which led the end-of-life date to March 2026.<ref name=":1">{{Cite web |title=Firefox Release Calendar |url=https://whattrainisitnow.com/calendar/ |website=Firefox Release Calendar |access-date=2024-09-20 |archive-url=https://web.archive.org/web/20240924091708/https://whattrainisitnow.com/calendar/ |archive-date=2024-09-24 |url-status=live}}</ref>

=== macOS ===
[[File:Firefox 136 screenshot, macOS Sonoma.png|thumb|Firefox 136 on [[macOS Sonoma]]]]<!-- That's a very old Firefox (and macOS) version, no longer supported, update? -->
The first official release (Firefox version 1.0) supported [[macOS]] (then called Mac OS X) on the [[PowerPC]] architecture. Mac OS X builds for the [[IA-32]] architecture became available via a [[universal binary]], which debuted with Firefox 1.5.0.2 in 2006.

Starting with version 4.0, Firefox was released for the x64 architecture, to which macOS had migrated.<ref name=maclinux64>{{cite web |url=https://www.mozilla.org/projects/firefox/3.7a5/releasenotes/ |title=Mozilla Developer Preview Alpha 5 Release Notes |publisher=Mozilla |date=June 14, 2010 |access-date=July 10, 2011 |archive-url=https://web.archive.org/web/20110629211729/http://www.mozilla.org/projects/firefox/3.7a5/releasenotes/ |archive-date=June 29, 2011}}</ref> Version 4.0 also dropped support for PowerPC architecture, although other projects continued development of a PowerPC version of Firefox.<ref>{{cite news |last=Gibbs |first=Samuel |date=April 27, 2011 |title=TenFourFox brings Firefox 4 to PPC Macs |url=https://www.engadget.com/2011-04-27-tenfourfox-brings-firefox-4-to-ppc-macs.html |work=Engadget |access-date=June 7, 2020 |archive-date=June 7, 2020 |archive-url=https://web.archive.org/web/20200607200413/https://www.engadget.com/2011-04-27-tenfourfox-brings-firefox-4-to-ppc-macs.html |url-status=live}}</ref>

Firefox was originally released for Mac OS X 10.0 and higher.<ref>{{cite web |url=http://www.mozilla.org/products/firefox/system-requirements.html |title=Firefox System Requirements |date=November 9, 2004 |access-date=June 7, 2020 |archive-url=https://web.archive.org/web/20041111034010/http://www.mozilla.org/products/firefox/system-requirements.html |archive-date=November 11, 2004}}</ref> The minimum OS then increased to Mac OS X 10.2 in Firefox 1.5 and 10.4 in Firefox 3.<ref>{{cite web |url=http://www.mozilla.com/firefox/system-requirements.html |title=Firefox System Requirements |date=November 29, 2005 |access-date=June 7, 2020 |archive-url=https://web.archive.org/web/20051215094626/http://www.mozilla.com/firefox/system-requirements.html |archive-date=December 15, 2005}}</ref><ref>{{cite web |url=https://www.firefox.com/en-US/firefox/3.0/system-requirements/ |title=Firefox 3.0 System Requirements |date=June 17, 2008 |access-date=November 14, 2025 |archive-url=https://web.archive.org/web/20200607200524/https://www.mozilla.org/en-US/firefox/3.0/system-requirements/ |archive-date=June 7, 2020 |url-status=live}}</ref> Firefox 4 dropped support for Mac OS X 10.4 and PowerPC Macs, and Firefox 17 dropped support for Mac OS X 10.5 entirely.<ref>{{cite web |url=https://www.firefox.com/en-US/firefox/4.0/system-requirements/ |title=Firefox 4.0 System Requirements |date=March 22, 2011 |access-date=November 14, 2025 |archive-url=https://web.archive.org/web/20200731154936/https://www.mozilla.org/en-US/firefox/4.0/system-requirements/ |archive-date=July 31, 2020 |url-status=live}}</ref><ref>{{cite web |url=https://www.firefox.com/en-US/firefox/17.0/system-requirements/ |title=Firefox 17.0 System Requirements |date=November 20, 2012 |access-date=November 14, 2025 |archive-url=https://web.archive.org/web/20200731154950/https://www.mozilla.org/en-US/firefox/17.0/system-requirements/ |archive-date=July 31, 2020 |url-status=live}}</ref> The system requirements were left unchanged until 2016, when Firefox 49 dropped support for Mac OS X 10.6–10.8.<ref>{{cite web |url=https://www.firefox.com/en-US/firefox/48.0/releasenotes/ |title=Firefox 48.0 Release Notes |date=August 2, 2016 |access-date=June 7, 2020 |archive-url=https://web.archive.org/web/20160920221127/https://www.mozilla.org/en-US/firefox/48.0/releasenotes/ |archive-date=September 20, 2016 |url-status=live}}</ref><ref>{{cite web |url=https://blog.mozilla.org/futurereleases/2016/04/29/update-on-firefox-support-for-os-x/ |title=Update on Firefox support for OS X |date=April 29, 2016 |access-date=June 7, 2020 |archive-url=https://web.archive.org/web/20200607200403/https://blog.mozilla.org/futurereleases/2016/04/29/update-on-firefox-support-for-os-x/ |archive-date=June 7, 2020 |url-status=live}}</ref> Mozilla ended support for OS X 10.9–10.11 in Firefox 79, with those users being supported on the Firefox 78 ESR branch until November 2021.<ref>{{cite web |url=https://blog.mozilla.org/futurereleases/2020/06/23/update-on-firefox-support-for-macos-10-9-10-10-and-10-11/ |title=Update on Firefox Support for macOS 10.9, 10.10 and 10.11 |date=June 23, 2020 |access-date=July 28, 2020 |archive-url=https://web.archive.org/web/20200721204255/https://blog.mozilla.org/futurereleases/2020/06/23/update-on-firefox-support-for-macos-10-9-10-10-and-10-11/ |archive-date=July 21, 2020 |url-status=live}}</ref><ref>{{cite web |url=https://www.firefox.com/en-US/firefox/78.0/releasenotes/ |title=Firefox 78 release notes |date=June 30, 2020 |access-date=November 14, 2025 |archive-url=https://web.archive.org/web/20200630133108/https://www.mozilla.org/en-US/firefox/78.0/releasenotes/ |archive-date=June 30, 2020 |url-status=live}}</ref><ref>{{cite web |url=https://www.firefox.com/en-US/firefox/79.0/system-requirements/ |title=Firefox 79 system requirements |date=July 28, 2020 |access-date=November 14, 2025 |archive-url=https://web.archive.org/web/20200728141256/https://www.mozilla.org/en-US/firefox/79.0/system-requirements/ |archive-date=July 28, 2020 |url-status=live}}</ref> Most recently, Mozilla ended support for [[macOS 10.12]]–[[macOS Mojave|10.14]] in Firefox 116, with those users being supported on the Firefox 115 ESR branch until late 2024. In September 2024, however, an extension was announced for the 115 ESR branch for an initial period of six months.<ref name=":2" /> This extension has been renewed twice, leading the end-of-life date to September 2025, and then to March 2026.<ref name=":1" />

=== Linux ===
[[File:Firefox 145.0 on Linux screenshot.webp|thumb|Firefox 145 on [[openSUSE]]]]
[[File:Firefox 136 on Fedora 41, browsing the English Wikipedia site.webm|thumb|Opening Wikipedia main page with Mozilla Firefox 136 on [[Fedora Linux]] 41]]
Since its inception, Firefox for Linux has supported the 32-bit memory architecture of the IA-32 instruction set. 64-bit builds were introduced in the 4.0 release.<ref name=maclinux64 /> The 46.0 release replaced [[GTK]] 2.18 with 3.4 as a system requirement on Linux and other systems running [[X.Org Server|X.Org]].<ref>{{cite web |url=https://www.mozilla.org/en-US/firefox/46.0/system-requirements/ |title=Firefox 46.0 System Requirements |website=Mozilla |access-date=February 26, 2018 |archive-url=https://web.archive.org/web/20180109063904/https://www.mozilla.org/en-US/firefox/46.0/system-requirements/ |archive-date=January 9, 2018 |url-status=live}}</ref> Starting with 53.0, the 32-bit builds required the [[SSE2]] instruction set.<ref>{{Cite web |title=Your hardware is no longer supported {{!}} Firefox Help |url=https://support.mozilla.org/en-US/kb/your-hardware-no-longer-supported |access-date=2024-06-10 |website=support.mozilla.org |archive-url=https://web.archive.org/web/20240610145042/https://support.mozilla.org/en-US/kb/your-hardware-no-longer-supported |archive-date=June 10, 2024 |url-status=live}}</ref>

Firefox 145 dropped support for 32-bit Linux on November 11, 2025, with those users being supported on the Firefox 140 ESR branch until September 2026.<ref>{{cite web |url=https://blog.mozilla.org/futurereleases/2025/09/05/firefox-32-bit-linux-support-to-end-in-2026/ |title=Firefox 32-bit Linux Support to End in 2026 - Future releases |website=blog.mozilla.org |date=September 5, 2025 |publisher=Mozilla Foundation |access-date=November 14, 2025 |archive-url=https://web.archive.org/web/20251011102740/https://blog.mozilla.org/futurereleases/2025/09/05/firefox-32-bit-linux-support-to-end-in-2026/ |archive-date=October 11, 2025 |url-status=live}}</ref>

====Firefox for ChromeOS====
[[ChromeOS]] is technically a Linux distribution, but it is so significant, it is listed anyway. Regardless, you can get Firefox on ChromeOS through the Google Play Store, going into terminal and typing Linux commands, or downloading a .deb file and loading Firefox.

=== Firefox for Android ===
{{Main|Firefox for Android}}

Firefox for mobile, code-named "Fennec", was first released for [[Maemo]] in January 2010 with version 1.0<ref>{{cite web |date=January 28, 2010 |title=Firefox for Nokia N900 Release Notes |url=https://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/mobile/1.0/releasenotes/ |access-date=February 9, 2012 |publisher=mozilla.org |archive-date=June 3, 2014 |archive-url=https://web.archive.org/web/20140603233726/http://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/mobile/1.0/releasenotes/ |url-status=live }}</ref> and for [[Android (operating system)|Android]] in March 2011 with version 4.0.<ref name="ff43">{{cite web |title=Mozilla Launches Firefox 4 for Android, Allowing Users to Take the Power and Customization of Firefox Everywhere |url=http://blog.mozilla.com/blog/2011/03/29/mozilla-launches-firefox-4-for-android-allowing-users-to-take-the-power-and-customization-of-firefox-everywhere-2/ |access-date=March 29, 2011 |archive-date=August 13, 2011 |archive-url=https://web.archive.org/web/20110813151427/http://blog.mozilla.com/blog/2011/03/29/mozilla-launches-firefox-4-for-android-allowing-users-to-take-the-power-and-customization-of-firefox-everywhere-2/ |url-status=live }}</ref> Support for Maemo was discontinued after version 7, released in September 2011.<ref>{{cite web |year=2013 |title=System Requirements – Firefox for Android 7.0 release notes |url=https://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/mobile/7.0/releasenotes/#system-requirements |access-date=March 28, 2015 |work=Mozilla website archive |publisher=Mozilla |archive-date=September 6, 2014 |archive-url=https://web.archive.org/web/20140906045226/http://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/mobile/7.0/releasenotes/#system-requirements |url-status=live }}</ref> Fennec had a user interface optimized for phones and tablets. It included the Awesome Bar, tabbed browsing, add-on support, a password manager, location-aware browsing, and the ability to synchronize with the user's other devices with Mozilla Firefox using [[Firefox Sync]].<ref>{{cite web |title=Firefox mobile features |publisher=Mozilla |url=https://www.mozilla.com/mobile/features/ |access-date=January 30, 2010}}</ref> At the end of its existence, it had a market share of 0.5% on Android.<ref>{{Cite web |title=Market share for mobile, browsers, operating systems and search engines {{!}} NetMarketShare |url=https://netmarketshare.com/?options=%7B%22filter%22:%7B%22$and%22:%5B%7B%22platform%22:%7B%22$in%22:%5B%22Android%22%5D%7D%7D%5D%7D,%22dateLabel%22:%22Custom%22,%22attributes%22:%22share%22,%22group%22:%22browser%22,%22sort%22:%7B%22share%22:-1%7D,%22id%22:%22browsersDesktop%22,%22dateInterval%22:%22Monthly%22,%22dateStart%22:%222018-06%22,%22dateEnd%22:%222020-05%22,%22segments%22:%22-1000%22%7D |access-date=September 6, 2020 |website=netmarketshare.com |archive-date=November 12, 2020 |archive-url=https://web.archive.org/web/20201112151351/https://netmarketshare.com/?options=%7B%22filter%22%3A%7B%22%24and%22%3A%5B%7B%22platform%22%3A%7B%22%24in%22%3A%5B%22Android%22%5D%7D%7D%5D%7D%2C%22dateLabel%22%3A%22Custom%22%2C%22attributes%22%3A%22share%22%2C%22group%22%3A%22browser%22%2C%22sort%22%3A%7B%22share%22%3A-1%7D%2C%22id%22%3A%22browsersDesktop%22%2C%22dateInterval%22%3A%22Monthly%22%2C%22dateStart%22%3A%222018-06%22%2C%22dateEnd%22%3A%222020-05%22%2C%22segments%22%3A%22-1000%22%7D |url-status=live}}</ref>

In August 2020, Mozilla launched a new version of its Firefox for Android app, named Firefox Daylight to the public<ref name="Zare">{{Cite web |last=Zare |first=Vesta |title=Fast, personalized and private by design on all platforms: introducing a new Firefox for Android experience |url=https://blog.mozilla.org/blog/2020/08/25/introducing-a-new-firefox-for-android-experience |url-status=live |archive-url=https://web.archive.org/web/20200905194022/https://blog.mozilla.org/blog/2020/08/25/introducing-a-new-firefox-for-android-experience/ |archive-date=September 5, 2020 |access-date=September 6, 2020 |website=The Mozilla Blog}}</ref> and codenamed [[Firefox for Android|Fenix]],<ref>{{Citation |title=mozilla-mobile/fenix |date=September 5, 2020 |url=https://github.com/mozilla-mobile/fenix |archive-url=https://web.archive.org/web/20200907140813/https://github.com/mozilla-mobile/fenix |publisher=Mozilla Mobile |access-date=September 6, 2020 |archive-date=September 7, 2020 |url-status=live}}</ref> after a little over a year of testing.<ref name="auto">{{Cite web |title=GeckoView in 2019 – Mozilla Hacks – the Web developer blog |url=https://hacks.mozilla.org/2019/06/geckoview-in-2019 |url-status=live |archive-url=https://web.archive.org/web/20200817152237/https://hacks.mozilla.org/2019/06/geckoview-in-2019/ |archive-date=August 17, 2020 |access-date=September 6, 2020 |website=Mozilla Hacks – the Web developer blog}}</ref> It boasted higher speeds with its new [[GeckoView]] engine, which is described as being "the only independent [[Browser engine|web engine browser]] available on [[Android (operating system)|Android]]". It also added Enhanced Tracking Protection 2.0, a feature that blocks many known [[Internet tracking|trackers]] on the Internet.<ref>{{Cite news |title=Firefox Launched a New Android App to Lure Users From Chrome |magazine=Wired |url=https://www.wired.co.uk/article/firefox-android-app-new-update-daylight |url-status=live |access-date=August 28, 2020 |archive-url=https://web.archive.org/web/20200827201914/https://www.wired.co.uk/article/firefox-android-app-new-update-daylight |archive-date=August 27, 2020 |issn=1059-1028}}</ref> It also added the ability to place the address bar on the bottom, and a new Collections feature.<ref name="Zare" /> However, it was criticized for only having nine [[Add-ons for Firefox|Add-ons]] at launch, and missing certain features.<ref>{{Cite web |date=September 1, 2020 |title=Latest Firefox Update Upsets Users Due To Missing Features |url=https://www.androidheadlines.com/2020/08/latest-firefox-update-upsets-users-features.html |url-status=live |archive-url=https://web.archive.org/web/20200905040145/https://www.androidheadlines.com/2020/08/latest-firefox-update-upsets-users-features.html |archive-date=September 5, 2020 |access-date=September 6, 2020 |website=Android Headlines}}</ref><ref>{{Cite news |date=August 7, 2020 |title=Three Reasons not to upgrade to the new Firefox for Android browser right now – gHacks Tech News |url=https://www.ghacks.net/2020/08/07/three-reasons-not-to-upgrade-to-the-new-firefox-for-android-browser-right-now/ |url-status=live |archive-url=https://web.archive.org/web/20200917204555/https://www.ghacks.net/2020/08/07/three-reasons-not-to-upgrade-to-the-new-firefox-for-android-browser-right-now/ |archive-date=September 17, 2020 |access-date=September 6, 2020 |newspaper=Ghacks Technology News}}</ref><ref>{{Cite web |last=Hellstrom |first=Jeremy |date=August 26, 2020 |title=Maybe Don't Update Firefox for Android |url=https://pcper.com/2020/08/maybe-dont-update-firefox-for-android/ |url-status=live |archive-url=https://web.archive.org/web/20200925032149/https://pcper.com/2020/08/maybe-dont-update-firefox-for-android/ |archive-date=September 25, 2020 |access-date=September 6, 2020 |website=[[PC Perspective]]}}</ref> In response, Mozilla stated that they will allow more Add-ons with time.<ref>{{Cite web |date=September 3, 2020 |title=Mozilla promises expanded extensions support following controversial Firefox Android update |url=https://www.androidpolice.com/2020/09/03/firefox-update-faces-backlash-due-to-missing-features-and-few-supported-extensions/ |url-status=live |archive-url=https://web.archive.org/web/20200905234334/https://www.androidpolice.com/2020/09/03/firefox-update-faces-backlash-due-to-missing-features-and-few-supported-extensions/ |archive-date=September 5, 2020 |access-date=September 6, 2020 |website=Android Police}}</ref>

{{Multiple image
| align = center
| direction = horizontal
| width = 200
| image1 = FennecMeeGo (cropped).png | caption1 = Firefox on [[MeeGo]] OS
| image2 = Firefox in firefox os.png | caption2 = Firefox on [[Firefox OS]]
| image3 = Firefox for Android 145.0 screenshot.webp | caption3 = Firefox 145 on [[Android (operating system)|Android]]
}}

{{Firefox for Android release compatibility}}

=== Firefox for iOS ===
[[File:Firefox for iOS 144 screenshot.png|thumb|right|190px|Firefox 144 on [[iOS]]]]
Mozilla initially refused to port Firefox to iOS due to the restrictions Apple imposed on third-party iOS browsers. Instead of releasing a full version of the Firefox browser, Mozilla released Firefox Home, a companion app for the iPhone and iPod Touch based on the [[Firefox Sync]] technology, which allowed users to access their Firefox browsing history, bookmarks, and recent tabs. It also included Firefox's "Awesomebar" location bar. Firefox Home was not a web browser, the application launched web pages in either an embedded viewer for that one page, or by opening the page in the Safari app.<ref>{{cite web |author=Dolecourt, Jessica |date=May 27, 2010 |title=Firefox Home: A not-quite Firefox iPhone app |url=http://reviews.cnet.com/8301-19512_7-20006090-233.html?tag=mncol |url-status=dead |archive-url=https://web.archive.org/web/20121023083335/http://reviews.cnet.com/8301-19512_7-20006090-233.html?tag=mncol |archive-date=October 23, 2012 |access-date=June 2, 2010}}</ref><ref>{{cite web |date=May 26, 2010 |title=Firefox Home Coming Soon to the iPhone |url=http://blog.mozilla.com/blog/2010/05/26/firefox-home-coming-soon-to-the-iphone/ |access-date=June 3, 2010 |archive-date=August 30, 2011 |archive-url=https://web.archive.org/web/20110830032230/http://blog.mozilla.com/blog/2010/05/26/firefox-home-coming-soon-to-the-iphone/ |url-status=live }}</ref> Mozilla pulled Firefox Home from the [[App Store (Apple)|App Store]] in September 2012, stating it would focus its resources on other projects. The company subsequently released the [[source code]] of Firefox Home's underlying synchronization software.<ref name="CW">{{cite web |last=Keizer |first=Gregg |date=September 4, 2012 |title=Mozilla exits iOS as it retires Firefox Home |url=http://www.computerworld.com/s/article/9230877/Mozilla_exits_iOS_as_it_retires_Firefox_Home |access-date=September 14, 2012 |work=Computerworld |archive-date=September 6, 2012 |archive-url=https://web.archive.org/web/20120906234343/http://www.computerworld.com/s/article/9230877/Mozilla_exits_iOS_as_it_retires_Firefox_Home |url-status=live }}</ref>

In April 2013, then-Mozilla CEO [[Gary Kovacs]] said that Firefox would not come to iOS if Apple required the use of the [[WebKit]] layout engine to do so. One reason given by Mozilla was that before [[iOS 8]], Apple had supplied third-party browsers with an inferior version of its JavaScript engine, which hobbled their performance, making it impossible to match Safari's JavaScript performance on the iOS platform.<ref>{{cite web |last=Bilton |first=Ricardo |date=March 10, 2013 |title=Mozilla wants to bring Firefox to iOS, but mean ol' Apple's standing in its way |url=https://venturebeat.com/2013/03/10/mozilla-firefox-ios/ |url-status=live |archive-url=https://web.archive.org/web/20161018233945/http://venturebeat.com/2013/03/10/mozilla-firefox-ios/ |archive-date=October 18, 2016 |access-date=September 18, 2016 |website=VentureBeat}}</ref> Apple later opened their "Nitro" JavaScript engine to third-party browsers.<ref>{{cite web |last=Shankland |first=Stephen |date=June 4, 2014 |title=iOS 8 grants new power to rival browsers, Web-based apps |url=https://www.cnet.com/news/ios-8-grants-new-power-to-rival-browsers-web-based-apps/ |url-status=live |archive-url=https://web.archive.org/web/20160901151602/http://www.cnet.com/news/ios-8-grants-new-power-to-rival-browsers-web-based-apps/ |archive-date=September 1, 2016 |access-date=September 18, 2016 |publisher=CNET}}</ref> In 2015, Mozilla announced it was moving forward with Firefox for iOS, with a preview release made available in New Zealand in September of that year.<ref>{{cite web |date=September 3, 2015 |title=Firefox for iOS Now Available for Preview |url=https://blog.mozilla.org/futurereleases/2015/09/03/firefox-for-ios-now-available-for-preview/ |url-status=live |archive-url=https://web.archive.org/web/20150904142955/https://blog.mozilla.org/futurereleases/2015/09/03/firefox-for-ios-now-available-for-preview/ |archive-date=September 4, 2015 |access-date=September 7, 2015}}</ref><ref>{{cite web |last=Clarke |first=Gavin |date=September 4, 2015 |title=Fruity Firefox: Mozilla caves to Apple, unveils iOS-friendly browser |url=https://www.theregister.co.uk/2015/09/04/mozilla_reveals_firefox_ios_preview_apple/ |url-status=live |archive-url=https://web.archive.org/web/20150906221803/http://www.theregister.co.uk/2015/09/04/mozilla_reveals_firefox_ios_preview_apple |archive-date=September 6, 2015 |access-date=September 7, 2015 |website=[[The Register]]}}</ref><ref>{{cite web |date=May 22, 2015 |title=Update on Firefox for iOS |url=https://blog.mozilla.org/futurereleases/2015/05/22/update-on-firefox-for-ios/ |url-status=live |archive-url=https://web.archive.org/web/20150905091030/https://blog.mozilla.org/futurereleases/2015/05/22/update-on-firefox-for-ios/ |archive-date=September 5, 2015 |access-date=September 7, 2015}}</ref> It was fully released in November later that year.<ref>{{Cite web |last=Calimlim |first=Aldrin |date=November 12, 2015 |title=Finally, Mozilla's Firefox Web browser is now available on iOS |url=http://appadvice.com/appnn/2015/11/finally-mozillas-firefox-web-browser-is-now-available-on-ios |url-status=live |archive-url=https://web.archive.org/web/20161005130721/http://appadvice.com/appnn/2015/11/finally-mozillas-firefox-web-browser-is-now-available-on-ios |archive-date=October 5, 2016 |access-date=September 6, 2020 |website=AppAdvice}}</ref> It is the first Firefox-branded browser not to use the [[Gecko (layout engine)|Gecko]] [[Browser engine|layout engine]] as is used in Firefox for [[Mozilla Firefox|desktop]] and [[Firefox for mobile|mobile]]. Apple's policies require all iOS apps that browse the web to use the built-in [[WebKit]] rendering framework and WebKit JavaScript, so using Gecko is not possible.<ref>{{Cite web |last=Porter |first=Jon |date=September 18, 2020 |title=Here are the browsers iOS 14 now lets you set as default |url=https://www.theverge.com/21444995/ios-14-default-browsers-chrome-edge-firefox-duckduckgo-safari |access-date=November 11, 2020 |website=The Verge |quote=All browsers are still required to use WebKit |archive-date=November 12, 2020 |archive-url=https://web.archive.org/web/20201112194054/https://www.theverge.com/21444995/ios-14-default-browsers-chrome-edge-firefox-duckduckgo-safari |url-status=live }}</ref><ref>{{cite web |date=September 12, 2019 |title=App Store Review Guidelines |url=https://developer.apple.com/app-store/review/guidelines/ |url-status=live |archive-url=https://web.archive.org/web/20200304025827/https://developer.apple.com/app-store/review/guidelines/ |archive-date=March 4, 2020 |access-date=November 11, 2020 |website=developer.apple.com |quote=2.5.6 Apps that browse the web must use the appropriate WebKit framework}}</ref> Unlike [[Firefox for Android|Firefox on Android]], Firefox for iOS does not support browser add-ons.

In November 2016, Firefox released a new iOS app titled [[Firefox Focus]], a private web browser.<ref>{{cite web |last=Perez |first=Sarah |date=November 17, 2016 |title=Mozilla launches Firefox Focus, a private web browser for iPhone |url=https://techcrunch.com/2016/11/17/mozilla-launches-firefox-focus-a-private-web-browser-for-iphone/ |url-status=live |archive-url=https://web.archive.org/web/20170510080834/https://techcrunch.com/2016/11/17/mozilla-launches-firefox-focus-a-private-web-browser-for-iphone/ |archive-date=May 10, 2017 |access-date=May 6, 2017 |website=[[TechCrunch]]}}</ref>

=== Firefox Reality (AR/VR) ===
Firefox Reality was released for [[augmented reality]] and [[virtual reality]] headsets in September 2018.<ref name="FirefoxReality">{{cite news |url=https://www.roadtovr.com/firefox-reality-vr-browser-launch-oculus-go-daydream-vive-focus/ |title='Firefox Reality', Mozilla's VR Web Browser, Launches on Major Standalone Headsets |archive-date=November 9, 2020 |access-date=October 1, 2020 |archive-url=https://web.archive.org/web/20201109034242/https://www.roadtovr.com/firefox-reality-vr-browser-launch-oculus-go-daydream-vive-focus/ |url-status=live}}</ref> It supports traditional web-browsing through 2D windows and immersive VR pages through [[WebVR|Web VR]]. Firefox Reality is available on [[HTC Vive]], [[Oculus (brand)|Oculus]], [[Google Daydream]] and [[Microsoft Hololens]] headsets. In February 2022, Mozilla announced that [[Igalia]] took over stewardship of this project under the new name of Wolvic.<ref>{{cite web |url=https://blog.mozilla.org/mozilla/update-on-firefox-reality/ |title=Update on Firefox Reality |access-date=December 22, 2022 |archive-date=July 7, 2022 |archive-url=https://web.archive.org/web/20220707141112/https://blog.mozilla.org/mozilla/update-on-firefox-reality/ |url-status=live }}</ref>

=== Third-party ports ===
Firefox has also been ported to [[FreeBSD]],<ref name="FreeBSD">{{cite web |url=https://www.freshports.org/www/firefox/ |title=FreeBSD port of Firefox |access-date=September 30, 2014 |archive-url=https://web.archive.org/web/20141005134424/http://www.freshports.org/www/firefox |archive-date=October 5, 2014 |url-status=live}}</ref> [[NetBSD]],<ref name="NetBSD1">{{cite web |url=https://pkgsrc.se/www/firefox/ |title=pkgsrc package of Firefox |access-date=December 10, 2021 |archive-url=https://web.archive.org/web/20210928164002/https://pkgsrc.se/www/firefox |archive-date=September 28, 2021 |url-status=live}}</ref> [[OpenBSD]],<ref name="OpenBSD">{{Cite web |url=http://ports.su/www/mozilla-firefox |title=OpenBSD ports ∴ www/mozilla-firefox |website=ports.su |access-date=December 23, 2014 |archive-url=https://web.archive.org/web/20141223055452/http://ports.su/www/mozilla-firefox |archive-date=December 23, 2014 |url-status=live}}</ref> [[OpenIndiana]],<ref name="OpenIndiana">[http://pkgsrc-repo.uk.openindiana.org/packages/www/firefox-l10n-3.6.15.tgz Source package of Firefox 3.6.15] {{webarchive |url=https://web.archive.org/web/20160304231602/http://pkgsrc-repo.uk.openindiana.org/packages/www/firefox-l10n-3.6.15.tgz |date=March 4, 2016 }}. pkgsrc-repo.uk.openindiana.org.</ref> [[OS/2]],<ref>{{Cite web |url=http://hobbes.nmsu.edu/h-viewer.php?dir=/pub/os2/apps/internet/www/browser&file=firefox-38.8.0.en-us.os2-wpi.wpi |title=[hobbes.nmsu.edu] Viewing file: /pub/os2/apps/internet/www/browser/firefox-38.8.0.en-us.os2-wpi.wpi |website=hobbes.nmsu.edu |access-date=October 18, 2016 |archive-url=https://web.archive.org/web/20170115064409/http://hobbes.nmsu.edu/h-viewer.php?dir=%2Fpub%2Fos2%2Fapps%2Finternet%2Fwww%2Fbrowser&file=firefox-38.8.0.en-us.os2-wpi.wpi |archive-date=January 15, 2017 |url-status=live}}</ref> [[ArcaOS]],<ref>{{cite news |url=https://www.arcanoae.com/arca-noaes-support-of-open-source-projects-firefox/ |title=Arca Noae's support of open source projects: Firefox |access-date=September 6, 2020 |newspaper=Arca Noae |date=June 8, 2016 |archive-date=September 20, 2020 |archive-url=https://web.archive.org/web/20200920115609/https://www.arcanoae.com/arca-noaes-support-of-open-source-projects-firefox/ |url-status=live |last1=Rosenthal |first1=Lewis }}</ref> [[SkyOS]], [[RISC OS]]<ref>{{Cite web |title=The Icon Bar: Firefox_released_for_RISC_OS_5_Updated: The Icon Bar: Firefox released for RISC OS 5 [Updated] |url=https://www.iconbar.com/Firefox_released_for_RISC_OS_5_Updated/news1097.html |access-date=January 20, 2021 |website=The Icon Bar |archive-date=August 13, 2021 |archive-url=https://web.archive.org/web/20210813112445/https://www.iconbar.com/Firefox_released_for_RISC_OS_5_Updated/news1097.html |url-status=live}}</ref> and [[BeOS]]/[[Haiku (operating system)|Haiku]],<ref>{{Cite web |url=https://www-archive.mozilla.org/ports/beos/ |title=Bezilla: Mozilla for BeOS |website=www-archive.mozilla.org |access-date=August 20, 2019 |archive-url=https://web.archive.org/web/20190820061412/https://www-archive.mozilla.org/ports/beos/ |archive-date=August 20, 2019 |url-status=live}}</ref><ref name="BeBytes">{{Cite web |url=http://www.be.wildman-productions.org/index.php?action=displaypage&pagename=appitem&appid=1 |title=BeBytes – The BeOS Software Archive |website=be.wildman-productions.org |access-date=August 20, 2019 |archive-url=https://web.archive.org/web/20190415061608/http://www.be.wildman-productions.org/index.php?action=displaypage&pagename=appitem&appid=1 |archive-date=April 15, 2019 |url-status=live}}</ref><ref name="BeBits1">{{Cite web |url=http://www.bebits.com/app/3143 |archive-url=https://web.archive.org/web/20120717032004/http://www.bebits.com/app/3143 |url-status=dead |title=Firefox entry on BeBits |archive-date=July 17, 2012}}</ref><ref name="BeBits2">{{Cite web |url=http://www.bebits.com/app/2715 |archive-url=https://web.archive.org/web/20120415005220/http://www.bebits.com/app/2715 |url-status=dead |title=Firefox Bleeding Edge entry on BeBits |archive-date=April 15, 2012}}</ref> and an unofficial rebranded version called [[Timberwolf (web browser)|Timberwolf]] has been available for [[AmigaOS 4]].<ref>{{Cite web |date=August 16, 2011 |title=Timberwolf Browser |url=https://www.amigaos.net/software/53/timberwolf-browser |access-date=December 24, 2022 |website=AmigaOS}}</ref>

The Firefox port for OpenBSD has been maintained by Landry Breuil since 2010. Firefox is regularly built for the current branch of the operating system; the latest versions are packaged for each release and remain frozen until the next release. In 2017, Landry began hosting packages of newer Firefox versions for OpenBSD releases from 6.0 onwards, making them available to installations without the ports system.<ref>{{cite web |url=https://undeadly.org/cgi?action=article&sid=20170425173917 |publisher=OpenBSD Journal |access-date=December 18, 2017 |date=April 25, 2017 |title=The many ways of running firefox on OpenBSD |archive-url=https://web.archive.org/web/20171228112231/https://undeadly.org/cgi?action=article&sid=20170425173917 |archive-date=December 28, 2017 |url-status=live}}</ref>

The [[Solaris (operating system)|Solaris]] 10 port of Firefox (including [[OpenSolaris]]) was maintained by the Oracle Solaris Desktop Beijing Team,<ref>{{cite web |url=https://ftp.mozilla.org/pub/firefox/releases/52.0.2esr/contrib/ |title=Directory Listing: /pub/firefox/releases/52.0.2esr/contrib/ |publisher=Ftp.mozilla.org |access-date=February 14, 2018 |archive-url=https://web.archive.org/web/20180215023333/https://ftp.mozilla.org/pub/firefox/releases/52.0.2esr/contrib/ |archive-date=February 15, 2018 |url-status=live}}</ref><ref>{{cite web |url=http://unixpackages.com/packages/mozilla |title=Mozilla – Firefox, Thunderbird & Sunbird |work=UNIX Packages - Open Source applications for Sun Solaris |date=December 21, 2011 |publisher=UNIX Packages |access-date=October 29, 2015 |archive-url=https://web.archive.org/web/20151208111945/https://unixpackages.com/packages/mozilla |archive-date=December 8, 2015 |url-status=live}}</ref> until March 2018 when the team was disbanded. There was also an unofficial port of [[Firefox 3.6]].x to [[IBM AIX]]<ref>{{cite web |url=http://www-03.ibm.com/systems/power/software/aix/browsers/ |title=IBM AIX: Web browsers for AIX |publisher=03.ibm.com |access-date=October 29, 2015 |archive-url=https://web.archive.org/web/20160105042100/http://www-03.ibm.com/systems/power/software/aix/browsers/ |archive-date=January 5, 2016}}</ref><ref>{{cite web |url=https://www-archive.mozilla.org/unix/aix.html |title=Mozilla on AIX FAQ |publisher=Archive.mozilla.org |access-date=October 29, 2015 |archive-url=https://web.archive.org/web/20150706074002/http://www-archive.mozilla.org/unix/aix.html |archive-date=July 6, 2015 |url-status=live}}</ref> and of v1.7.x to [[UnixWare]].<ref>{{cite web |url=http://ftp.sco.com/pub/unixware7/714/other/mozilla_1_7_13a/UW7.README.html |title=README Mozilla, v. 1.7.13 for SCO(R) UnixWare(R) 7.1.3 SCO(R) UnixWare(R) 7.1.4 |publisher=Ftp.sco.com |date=June 6, 2005 |access-date=October 29, 2015 |archive-date=January 2, 2022 |archive-url=https://web.archive.org/web/20220102180451/http://ftp.sco.com/pub/unixware7/714/other/mozilla_1_7_13a/UW7.README.html |url-status=dead}}</ref>

{{Firefox contrib release compatibility}}

== Channels and release schedule ==
In March 2011, Mozilla presented plans to switch to the [[Firefox Rapid Release Model|rapid release model]], a faster 16-week [[development cycle]], similar to [[Google Chrome]]. ''[[Ars Technica]]'' noted that this new cycle entailed "significant technical and operational challenges" for Mozilla (notably preserving third-party [[Add-on (Mozilla)|add-on]] compatibility), but that it would help accelerate Firefox's adoption of new web standards, features, and performance improvements.<ref name="PaulRyan">{{Cite web |last=Paul |first=Ryan |date=March 18, 2011 |title=Mozilla outlines 16-week Firefox development cycle |url=https://arstechnica.com/information-technology/2011/03/mozilla-outlines-16-week-firefox-development-cycle/ |access-date=April 22, 2023 |website=Ars Technica |archive-date=April 22, 2023 |archive-url=https://web.archive.org/web/20230422162557/https://arstechnica.com/information-technology/2011/03/mozilla-outlines-16-week-firefox-development-cycle/ |url-status=live }}</ref><ref>{{Cite web |last=Paul |first=Ryan |date=February 14, 2011 |title=Is Mozilla's 2011 roadmap unrealistically ambitious? |url=https://arstechnica.com/information-technology/2011/02/is-mozillas-2011-roadmap-unrealistically-ambitious/ |access-date=April 22, 2023 |website=Ars Technica |archive-date=April 22, 2023 |archive-url=https://web.archive.org/web/20230422162558/https://arstechnica.com/information-technology/2011/02/is-mozillas-2011-roadmap-unrealistically-ambitious/ |url-status=live }}</ref> This plan was implemented in April 2011.<ref>{{Cite web |last=Siegler |first=M. G. |date=April 13, 2011 |title=Mozilla Introduces Aurora, The Pre-Beta, Post-Nightly Firefox — It's Their "Dev" Build |url=https://techcrunch.com/2011/04/13/mozilla-aurora/ |access-date=April 22, 2023 |website=TechCrunch |archive-date=April 22, 2023 |archive-url=https://web.archive.org/web/20230422162557/https://techcrunch.com/2011/04/13/mozilla-aurora/ |url-status=live }}</ref> The release process was split into four "channels", with major releases trickling down to the next channel every six to eight weeks. For example, the Nightly channel would feature a preliminary unstable version of Firefox 6, which would move to the experimental "Aurora" channel after preliminary testing, then to the more stable "beta" channel, before finally reaching the public release channel, with each stage taking around six weeks.<ref name="auto1">{{Cite web |last=Anthony |first=Sebastian |date=April 18, 2017 |title=Firefox kills off Aurora channel to speed up release of new features |url=https://arstechnica.com/information-technology/2017/04/firefox-aurora-killed-off/ |access-date=April 22, 2023 |website=Ars Technica |archive-date=April 22, 2023 |archive-url=https://web.archive.org/web/20230422162557/https://arstechnica.com/information-technology/2017/04/firefox-aurora-killed-off/ |url-status=live }}</ref><ref name="PaulRyan" /><ref>{{Cite magazine |date=April 14, 2011 |title=How to Use Firefox's New 'Aurora' Release Channel |magazine=Wired |url=https://www.wired.com/2011/04/how-to-use-firefoxs-new-aurora-release-channel/ |access-date=April 22, 2023 |issn=1059-1028}}</ref> For corporations, Mozilla introduced an Extended Support Release (ESR) channel, with new versions released every 30 weeks (and supported for 12 more weeks after a new ESR version is released), though Mozilla warned that it would be less secure than the release channel, since security patches would only be [[Backporting|backported]] for high-impact vulnerabilities.<ref>{{Cite web |last=Kingsley-Hughes |first=Adrian |date=September 22, 2011 |title=Mozilla attempts to appease enterprise users with talk of 42-week Firefox release cycle |url=https://www.zdnet.com/article/mozilla-attempts-to-appease-enterprise-users-with-talk-of-42-week-firefox-release-cycle/ |access-date=April 22, 2023 |publisher=ZDNet |archive-date=April 22, 2023 |archive-url=https://web.archive.org/web/20230422162557/https://www.zdnet.com/article/mozilla-attempts-to-appease-enterprise-users-with-talk-of-42-week-firefox-release-cycle/ |url-status=live }}</ref><ref>{{cite news |last=Paul |first=Ryan |title=Firefox extended support will mitigate rapid release challenges |publisher=ArsTechnica |date=January 10, 2012 |url=https://arstechnica.com/business/news/2012/01/firefox-extended-support-will-mitigate-rapid-release-challenges.ars |access-date=April 4, 2012 |archive-url=https://web.archive.org/web/20120412001748/http://arstechnica.com/business/news/2012/01/firefox-extended-support-will-mitigate-rapid-release-challenges.ars |archive-date=April 12, 2012 |url-status=live}}</ref>

In 2017, Mozilla abandoned the Aurora channel, which saw low uptake, and [[Rebasing|rebased]] Firefox Developer Edition onto the beta channel.<ref>{{Cite web |last=Protalinski |first=Emil |date=April 17, 2017 |title=Mozilla kills Firefox Aurora channel, builds will move directly from Nightly to Beta |url=https://venturebeat.com/business/mozilla-kills-firefox-aurora-channel-builds-will-move-directly-from-nightly-to-beta/ |access-date=April 22, 2023 |website=VentureBeat |archive-date=April 22, 2023 |archive-url=https://web.archive.org/web/20230422162557/https://venturebeat.com/business/mozilla-kills-firefox-aurora-channel-builds-will-move-directly-from-nightly-to-beta/ |url-status=live }}</ref> Mozilla uses [[A/B testing]]<ref>{{Cite web |last1=Kothari |first1=Ritu |last2=Or |first2=Yan |date=September 17, 2019 |title=Moving Firefox to a faster 4-week release cycle |url=https://hacks.mozilla.org/2019/09/moving-firefox-to-a-faster-4-week-release-cycle |access-date=April 22, 2023 |website=Mozilla |archive-date=May 21, 2023 |archive-url=https://web.archive.org/web/20230521004831/https://hacks.mozilla.org/2019/09/moving-firefox-to-a-faster-4-week-release-cycle/ |url-status=live }}</ref> and a staged rollout mechanism for the release channel, where updates are first presented to a small fraction of users, with Mozilla monitoring its telemetry for increased crashes or other issues before the update is made available to all users.<ref name="auto1"/> In 2020, Firefox moved to a four-week release cycle, to catch up with Chrome in support for new web features.<ref>{{Cite web |last=Cimpanu |first=Catalin |date=September 17, 2019 |title=Mozilla to release a new Firefox version every four weeks starting next year |url=https://www.zdnet.com/article/mozilla-to-release-a-new-firefox-version-every-four-weeks-starting-next-year/ |access-date=April 22, 2023 |publisher=ZDNet |archive-date=April 22, 2023 |archive-url=https://web.archive.org/web/20230422164059/https://www.zdnet.com/article/mozilla-to-release-a-new-firefox-version-every-four-weeks-starting-next-year/ |url-status=live }}</ref><ref>{{Cite web |last=Protalinski |first=Emil |date=January 7, 2020 |title=Firefox 72 arrives with fingerprinting blocked by default, Picture-in-Picture on macOS and Linux |url=https://venturebeat.com/business/mozilla-firefox-72/ |access-date=April 22, 2023 |website=VentureBeat |archive-date=April 22, 2023 |archive-url=https://web.archive.org/web/20230422164101/https://venturebeat.com/business/mozilla-firefox-72/ |url-status=live }}</ref> Chrome switched to a four-week cycle a year later.<ref>{{Cite web |last=Lardinois |first=Frederic |date=March 4, 2021 |title=Google speeds up its release cycle for Chrome |url=https://techcrunch.com/2021/03/04/google-speeds-up-its-release-cycle-for-chrome/ |access-date=April 22, 2023 |website=TechCrunch |archive-date=April 22, 2023 |archive-url=https://web.archive.org/web/20230422162557/https://techcrunch.com/2021/03/04/google-speeds-up-its-release-cycle-for-chrome/ |url-status=live }}</ref>

== Licensing ==
Firefox [[source code]] is [[free software]], with most of it being released under the [[Mozilla Public License]] (MPL) version 2.0.<ref name="Licensing-Policies">{{citation |url=https://www.mozilla.org/foundation/licensing.html |title=Mozilla Licensing Policies |publisher=mozilla.org |access-date=January 5, 2012 |archive-url=https://web.archive.org/web/20130402181908/http://www.mozilla.org/foundation/licensing.html |archive-date=April 2, 2013 |url-status=live}}</ref> This license permits anyone to view, modify, or redistribute the source code. As a result, several publicly released applications have been built from it, including Firefox's predecessor [[Netscape (web browser)|Netscape]],<ref>{{Cite web |title=The fall of Firefox: Mozilla's once-popular web browser slides into irrelevance |url=https://www.zdnet.com/home-and-office/networking/the-fall-of-firefox-mozillas-once-popular-web-browser-slides-into-irrelevance/ |access-date=2024-06-06 |website=ZDNET |archive-date=June 6, 2024 |archive-url=https://web.archive.org/web/20240606052649/https://www.zdnet.com/home-and-office/networking/the-fall-of-firefox-mozillas-once-popular-web-browser-slides-into-irrelevance/ |url-status=live }}</ref> the customizable [[Pale Moon]], and the privacy focused [[Tor Browser]].<ref>{{Cite journal |last1=Davitt |first1=Killian |last2=Ristea |first2=Dan |last3=Russell |first3=Duncan |last4=Murdoch |first4=Steven J. |date=2024 |title=CoStricTor: Collaborative HTTP Strict Transport Security in Tor Browser |url=https://petsymposium.org/popets/2024/popets-2024-0020.php |journal=Proceedings on Privacy Enhancing Technologies |page=345 |doi=10.56553/popets-2024-0020 |issn=2299-0984 |access-date=June 6, 2024 |archive-date=June 6, 2024 |archive-url=https://web.archive.org/web/20240606052649/https://petsymposium.org/popets/2024/popets-2024-0020.php |url-status=live |doi-access=free }}</ref>

In the past, Firefox was licensed solely under the MPL, then version 1.1,<ref name=mozrelicensing>{{cite web |url=https://www-archive.mozilla.org/MPL/relicensing-faq.html |title=Mozilla Relicensing FAQ |access-date=January 24, 2007 |publisher=Mozilla |archive-url=https://web.archive.org/web/20100513062601/http://www-archive.mozilla.org/MPL/relicensing-faq.html |archive-date=May 13, 2010}}</ref> which the [[Free Software Foundation]] criticized for being [[weak copyleft]], as the license permitted, in limited ways, proprietary [[derivative work]]s. Additionally, code only licensed under MPL 1.1 could not legally be linked with code under the [[GPL]].<ref>{{cite web |url=https://www.gnu.org/philosophy/netscape-npl.html |title=On the Netscape Public License |access-date=January 24, 2007 |last=Stallman |first=Richard |author-link=Richard Stallman |publisher=[[Free Software Foundation]] |archive-url=https://web.archive.org/web/20070203202915/http://www.gnu.org/philosophy/netscape-npl.html |archive-date=February 3, 2007 |url-status=live}}</ref><ref>{{cite web |url=https://www.gnu.org/licenses/license-list.html#MPL |title=Various Licenses and Comments about Them. Mozilla Public License (MPL) |access-date=January 24, 2007 |publisher=[[Free Software Foundation]] |archive-url=https://web.archive.org/web/20100724023833/https://www.gnu.org/licenses/license-list.html#MPL |archive-date=July 24, 2010 |url-status=live}}</ref> To address these concerns, Mozilla re-licensed most of Firefox under the [[tri-license]] scheme of MPL 1.1, GPL 2.0, or [[LGPL]] 2.1. Since the re-licensing, developers were free to choose the license under which they received most of the code, to suit their intended use: GPL or LGPL linking and derivative works when one of those licenses is chosen, or MPL use (including the possibility of proprietary derivative works) if they chose the MPL.<ref name=mozrelicensing /> However, Mozilla released the GPL-compatible MPL 2.0<ref>{{cite web | url=https://wiki.mozilla.org/MPL_Upgrade | title=MPL 2 Upgrade | access-date=2025-09-24}}</ref> on January 3, 2012,<ref>{{cite web |title=Announcing Version 2.0 of the Mozilla Public License |publisher=[[Mozilla]] |date=January 3, 2012 |url=https://mpl.mozilla.org/2012/01/03/announcing-mpl-2-0 |access-date=June 6, 2012 |archive-url=https://web.archive.org/web/20120306113159/http://mpl.mozilla.org/2012/01/03/announcing-mpl-2-0/ |archive-date=March 6, 2012}}</ref> and with the release of Firefox 13 on June 5, 2012, Mozilla used it to replace the tri-licensing scheme.<ref>{{cite news |url=http://www.h-online.com/open/news/item/Firefox-13-released-now-using-SPDY-by-default-1605039.html |title=Firefox 13 released – now using SPDY by default |date=June 5, 2012 |publisher=The H – Open |archive-url=https://web.archive.org/web/20120607032245/http://www.h-online.com/open/news/item/Firefox-13-released-now-using-SPDY-by-default-1605039.html |archive-date=June 7, 2012 |url-status=dead| quote=The licencing on Firefox 13 has also changed. Now, rather than the old MPL 1.1 and disjunctive tri-licence, Firefox source and binaries are released under the Mozilla Public Licence 2.0.| access-date=2025-09-24}}</ref>

== Trademark and logo ==
{{See also|Debian–Mozilla trademark dispute}}

The name "Mozilla Firefox" is a [[registered trademark symbol|registered trademark]] of Mozilla; along with the official Firefox logo, it may only be used under certain terms and conditions. Anyone may redistribute the official binaries in unmodified form and use the Firefox name and branding for such distribution, but restrictions are placed on distributions that modify the underlying source code.<ref>{{cite web |url=https://www.mozilla.org/foundation/trademarks/policy.html |title=Mozilla Trademark Policy |access-date=January 30, 2007 |publisher=Mozilla |archive-url=https://web.archive.org/web/20070128203012/http://www.mozilla.org/foundation/trademarks/policy.html |archive-date=January 28, 2007 |url-status=live}}</ref> The name "Firefox" derives from a nickname of the [[red panda]].<ref name="Firefox name FAQ" /> Mozilla celebrated Red Pandas.<ref>{{Cite web |title=Celebrating 20 years of Firefox with 20 red panda cams |url=https://blog.mozilla.org/en/products/firefox/red-panda-cams/ |access-date=2024-12-09 |website=The Mozilla Blog}}</ref>

Mozilla has placed the Firefox logo files under open-source licenses,<ref>{{Cite web |url=https://mxr.mozilla.org/mozilla-central/source/browser/branding/official/LICENSE |title=MXR is retired |website=mxr.mozilla.org |access-date=June 18, 2018 |archive-url=https://web.archive.org/web/20181105160726/https://mxr.mozilla.org/mozilla-central/source/browser/branding/official/LICENSE |archive-date=November 5, 2018 |url-status=live}}</ref><ref>{{Cite web |url=https://bugzilla.mozilla.org/show_bug.cgi?id=541761 |title=541761 – Some text implies the Firefox logo is under a non-free copyright license |website=bugzilla.mozilla.org |access-date=January 10, 2012 |archive-url=https://web.archive.org/web/20130420225505/https://bugzilla.mozilla.org/show_bug.cgi?id=541761 |archive-date=April 20, 2013 |url-status=live}}</ref> but its trademark guidelines do not allow displaying altered<ref name=MozComLegalStuff>{{cite web |url=https://www.mozilla.com/about/logo/legal.html |title=Legal Stuff |access-date=March 7, 2009 |publisher=Mozilla Corp |archive-url=https://web.archive.org/web/20130730224539/http://blog.mozilla.org/press/media-library/ |archive-date=July 30, 2013}}</ref> or similar logos<ref name=MozComStopLogo>{{cite web |title=Stop Logo Cruelty |publisher=Mozilla Corp. |url=https://www.mozilla.com/about/logo/stop.html |access-date=March 7, 2009 |archive-url=https://web.archive.org/web/20100522010026/http://www.mozilla.com/en-US/about/logo/stop.html |archive-date=May 22, 2010}} ''"'''Don't''' Create new elements that look enough like the Firefox logo so as to cause confusion."''</ref> in contexts where trademark law applies.<ref name="Mozilla Trademark Guidelines">{{Cite web |title=Mozilla Trademark Guidelines |url=https://www.mozilla.org/en-US/foundation/trademarks/policy/ |access-date=2024-05-24 |website=Mozilla |archive-date=June 14, 2018 |archive-url=https://web.archive.org/web/20180614232741/https://www.mozilla.org/en-US/foundation/trademarks/policy/ |url-status=live }}</ref>

[[File:Iceweasel icon.svg|thumb|upright|Logo used for [[Iceweasel]] ]]
There has been some controversy over the Mozilla Foundation's intentions in stopping certain open-source distributions from using the "Firefox" trademark.<ref name=LWNtrademark /> Open-source browsers "enable greater choice and innovation in the market rather than aiming for mass-market domination."<ref name="Krishnamurthy-2009" /> Mozilla Foundation Chairperson [[Mitchell Baker]] explained in an interview in 2007 that distributions could freely use the Firefox trademark if they did not modify source code, and that the Mozilla Foundation's only concern was with users getting a consistent experience when they used "Firefox".<ref>{{cite news |first=Dan |last=Warne |title=The stoush over Linux distributions using the Firefox trademark |work=APC Magazine |publisher=ACP Magazines Ltd |date=May 7, 2007 |url=http://apcmag.com/the_stoush_over_linux_distributions_using_the_firefox_trademark.htm |access-date=January 18, 2008 |archive-url=https://web.archive.org/web/20110817064956/http://apcmag.com/the_stoush_over_linux_distributions_using_the_firefox_trademark.htm |archive-date=August 17, 2011 |url-status=live}}</ref>

To allow distributions of the code ''without'' using the official branding, the Firefox [[build system]] contains a "branding switch". This switch, often used for alphas ("Auroras") of future Firefox versions, allows the code to be compiled without the official logo and name and can allow a derivative work unencumbered by restrictions on the Firefox trademark to be produced. In the unbranded build, the trademarked logo and name are replaced with a freely distributable generic globe logo and the name of the release series from which the modified version was derived.{{Citation needed|date=September 2020}}

Distributing modified versions of Firefox under the "Firefox" name required explicit approval from Mozilla for the changes made to the underlying code, and required the use of ''all'' of the official branding. For example, it was not permissible to use the name "Firefox" without also using the official logo. When the [[Debian]] project decided to stop using the official Firefox logo in 2006 (because Mozilla's copyright restrictions at the time were incompatible with [[Debian Free Software Guidelines|Debian's guidelines]]), they were told by a representative of the Mozilla Foundation that this was not acceptable and was asked either to comply with the published trademark guidelines or cease using the "Firefox" name in their distribution.<ref>{{cite web |url=https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=354622 |title=Debian Bug report logs – #354622: Uses Mozilla Firefox trademark without permission |publisher=Debian |access-date=January 30, 2007 |archive-url=https://web.archive.org/web/20130206164312/http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=354622 |archive-date=February 6, 2013 |url-status=live}}</ref> <!-- is this important enough to include in the context of this article? - Some Debian developers had misunderstood previous communication to be an agreement that allowed them to do this, but Mozilla disputed this assertion. --> Debian switched to branding their modified version of Firefox "[[Iceweasel]]" (but in 2016 switched back to Firefox), along with other Mozilla software. [[GNU IceCat]] is another derived version of Firefox distributed by the [[GNU Project]], which maintains its separate branding.<ref>{{cite web |url=https://lists.gnu.org/archive/html/bug-gnuzilla/2007-09/msg00004.html |title=Re: ice weasel |date=September 23, 2007 |access-date=July 6, 2018 |archive-url=https://web.archive.org/web/20180706183225/http://lists.gnu.org/archive/html/bug-gnuzilla/2007-09/msg00004.html |archive-date=July 6, 2018 |url-status=live}}</ref>

=== Branding and visual identity ===
{{Main|Firefox logo}}

The Firefox icon is a trademark used to designate the official Mozilla build of the Firefox software and builds of official distribution partners.<ref>[https://www.mozilla.org/foundation/trademarks/distribution-policy.html Mozilla Trademark Policy for Distribution Partners] {{Webarchive|url=https://web.archive.org/web/20130402194222/https://www.mozilla.org/foundation/trademarks/distribution-policy.html |date=April 2, 2013 }} Version 0.9 (DRAFT). Retrieved November 2, 2006.</ref> For this reason, software distributors who distribute modified versions of Firefox do not use the icon.<ref name="Mozilla Trademark Guidelines"/>

Early Firebird and Phoenix releases of Firefox were considered to have reasonable visual designs but fell short when compared to many other professional software packages. In October 2003, professional interface designer Steven Garrity authored an article covering everything he considered to be wrong with Mozilla's visual identity.<ref name="branding-mozilla">{{cite web |last=Garrity |first=Steven |title=Branding Mozilla: Towards Mozilla 2.0 |url=http://www.actsofvolition.com/files/mozillabranding/ |access-date=February 8, 2009 |date=October 23, 2003 |archive-url=https://web.archive.org/web/20090115202336/http://www.actsofvolition.com/files/mozillabranding/ |archive-date=January 15, 2009 |url-status=live}}</ref>

Shortly afterwards, the Mozilla Foundation invited Garrity to head up the new visual identity team. The release of Firefox 0.8 in February 2004 saw the introduction of the new branding efforts. Included were new icon designs by silverorange, a group of web developers with a long-standing relationship with Mozilla. The final renderings are by [[Jon Hicks (designer)|Jon Hicks]], who had worked on [[Camino (web browser)|Camino]].<ref name="branding-mozilla-followup">{{cite web |url=http://www.actsofvolition.com/archive/2004/february/brandingmozilla |title=Branding Mozilla: Towards Firefox 1.0 |last=Garrity |first=Steven |date=February 9, 2004 |access-date=February 8, 2009 |archive-url=https://web.archive.org/web/20090205043028/http://www.actsofvolition.com/archive/2004/february/brandingmozilla |archive-date=February 5, 2009 |url-status=live}}</ref><ref name="branding-firefox">{{cite web |url=https://www.hicksdesign.co.uk/journal/branding-firefox |title=Branding Firefox |last=Hicks |first=Jon |date=February 9, 2004 |publisher=Hicksdesign |access-date=February 8, 2009 |archive-url=https://web.archive.org/web/20090208065605/http://hicksdesign.co.uk/journal/branding-firefox |archive-date=February 8, 2009 |url-status=live}}</ref> The logo was later revised and updated, fixing several flaws found when it was enlarged.<ref name="spot-the-difference">{{cite web |url=https://www.hicksdesign.co.uk/journal/spot-the-difference/ |title=Spot the Difference |last=Hicks |first=Jon |date=December 17, 2004 |publisher=Hicksdesign |access-date=February 8, 2009 |archive-url=https://web.archive.org/web/20090205061152/http://www.hicksdesign.co.uk/journal/spot-the-difference/ |archive-date=February 5, 2009 |url-status=live}}</ref> The animal shown in the logo is a stylized fox, although "firefox" is usually a common name for the [[red panda]]. The panda, according to Hicks, "didn't really conjure up the right imagery" and was not widely known.<ref name="branding-firefox" />

In 2017, Mozilla made a sleeker, newer design of the Firefox logo as part of the quantum update.

In June 2019, Mozilla unveiled a revised Firefox logo, which was officially implemented on version 70. The new logo is part of an effort to build a brand system around Firefox and its complementary apps and services, which are now being promoted as a suite under the Firefox brand.

<gallery style="text-align:center" caption="Logo history">
File:Mozilla Phoenix logo vector.svg|Logo of "Phoenix" and "Firebird" before being renamed as Firefox
File:Mozilla Firefox 0.8 logo.svg|Firefox 0.8–0.10, from February 9, 2004, to November 8, 2004
File:Mozilla Firefox logo 2004.svg|Firefox 1.0–3.0, from November 9, 2004, to June 29, 2009
File:Mozilla Firefox 3.5 logo.png|Firefox 3.5–22, from June 30, 2009, to August 5, 2013
File:Mozilla Firefox logo 2013.svg|Firefox 23–56, from August 6, 2013 to November 13, 2017<ref>{{cite web |last=Martell |first=Sean |title=(Re)building a simplified Firefox logo |url=http://blog.seanmartell.com/2013/06/27/rebuilding-a-simplified-firefox-logo/ |work=Reticulating Splines |access-date=September 5, 2013 |date=June 27, 2013 |archive-url=https://web.archive.org/web/20130702182008/http://blog.seanmartell.com/2013/06/27/rebuilding-a-simplified-firefox-logo/ |archive-date=July 2, 2013 |url-status=live}}</ref>
File:Firefox Logo, 2017.svg|Firefox 57–69, from November 14, 2017, to October 21, 2019
File:Firefox logo, 2019.svg|Firefox 70 or later, since October 22, 2019
</gallery>

<gallery style="text-align:center;margin:0 auto" heights="110" widths="110" caption="Other logos, used for nightly versions">
File:Mozilla Nightly icon 2011.png|The 2011 Nightly logo, used to represent [[nightly build]]s of [[pre-alpha version]]s
File:Mozilla Firefox Nightly logo 2013.png|The 2013 Nightly logo
File:Firefox Nightly Logo, 2017.svg|The 2017 Nightly logo
File:Firefox Nightly logo, 2019.svg|The 2019 Nightly logo
</gallery>
<gallery style="text-align:center;margin:0 auto" heights="110" widths="110" caption="Other logos, used for developer/aurora versions">
File:Mozilla Aurora icon.png|The 2011 Aurora logo, used to represent an [[alpha release]]
File:Mozilla Firefox Aurora logo 2013.png|The 2013 Aurora logo
File:Firefox Developer Edition logo, 2013.png|The 2015 Developer Edition logo
File:Firefox Developer Edition logo, 2017.svg|The 2017 Developer Edition logo
File:Firefox Developer Edition logo,2019.svg|The 2019 Developer Edition logo
</gallery>

<gallery style="text-align:center;margin:0 auto" heights="110" widths="110" caption="Other logos">
File:Deer park globe.svg|Blue globe artwork, distributed with the [[source code]], and is explicitly not protected as a trademark<ref>[https://www.mozilla.org/foundation/trademarks/faq.html Mozilla Trademark Policy FAQ] {{Webarchive|url=https://web.archive.org/web/20130407213521/http://www.mozilla.org/foundation/trademarks/faq.html|date=April 7, 2013 }}: "What are the Mozilla Trademarks and Logos?". Retrieved November 2, 2006</ref>
File:Firefox brand logo, 2019.svg|The logo for the Firefox brand of products and services, as of July 2019.
</gallery>

== Promotion ==
[[File:Firefox mascot - FISL 16.jpg|thumb|Firefox mascot at the [[FISL]]{{nbsp}}16 (2015), Brazil]]

Firefox was adopted rapidly, with 100&nbsp;million downloads in its first year of availability.<ref>{{cite web |last1=Palmer |first1=Judi |last2=Colvig |first2=Mary |title=Firefox surpasses 100 million downloads |publisher=Mozilla |date=October 19, 2005 |url=https://www-archive.mozilla.org/press/mozilla-2005-10-19.html |access-date=February 4, 2007 |archive-url=https://web.archive.org/web/20090621002130/http://www-archive.mozilla.org/press/mozilla-2005-10-19.html |archive-date=June 21, 2009 |url-status=live}}</ref> This was followed by a series of aggressive marketing campaigns starting in 2004 with a series of events [[Blake Ross]] and Asa Dotzler called "marketing weeks".<ref>{{cite web |last=Ross |first=Blake |author-link=Blake Ross |title=Week 1: Press reviews |publisher=Blake Ross |date=July 7, 2004 |url=http://www.blakeross.com/archives/000228.html |archive-url=https://web.archive.org/web/20040805210701/http://www.blakeross.com/archives/000228.html |archive-date=August 5, 2004 |access-date=February 4, 2007}}</ref>

Firefox continued to heavily market itself by releasing a marketing portal dubbed "Spread Firefox" (SFX) on September 12, 2004.<ref>{{cite web |work=Spread Firefox: Sfx Team's Blog |title=We're igniting the web. Join us! |date=September 12, 2004 |url=http://www.spreadfirefox.com/node/115 |archive-url=https://web.archive.org/web/20070125002055/http://www.spreadfirefox.com/node/115 |archive-date=January 25, 2007 |access-date=February 4, 2007}}</ref> It debuted along with the Firefox Preview Release, creating a centralized space for the discussion of various marketing techniques. The release of their [[Mozilla Manifesto|manifesto]] stated that "the Mozilla project is a global community of people who believe that openness, innovation, and opportunity are key to the continued health of the Internet."<ref name="Krishnamurthy-2009">{{cite journal |last=Krishnamurthy |first=Sandeep |date=August 1, 2009 |title=CASE: Mozilla vs. Godzilla — The Launch of the Mozilla Firefox Browser |journal=Journal of Interactive Marketing |volume=23 |issue=3 |pages=259–271 |doi=10.1016/j.intmar.2009.04.008|s2cid=167784443  |issn = 1094-9968 }}</ref> A two-page ad in the edition of December 16 of ''The New York Times'', placed by Mozilla Foundation in coordination with Spread Firefox, featured the names of the thousands of people worldwide who contributed to the Mozilla Foundation's fundraising campaign to support the launch of the Firefox 1.0 web browser.<ref name="Mozilla Foundation">{{cite web |url=https://blog.mozilla.org/press/files/2013/11/nytimes-firefox-final.pdf |title=Mozilla Foundation Places Two-Page Advocacy Ad in the New York Times |date=December 15, 2004 |publisher=Mozilla Foundation |archive-url=https://web.archive.org/web/20180628015444/https://blog.mozilla.org/press/files/2013/11/nytimes-firefox-final.pdf |archive-date=June 28, 2018 |url-status=live |access-date=June 15, 2010}}</ref> SFX portal enhanced the "Get Firefox" button program, giving users "referrer points" as an incentive. The site lists the top 250 referrers. From time to time, the SFX team or SFX members launch marketing events organized at the Spread Firefox website. As a part of the Spread Firefox campaign, there was an attempt to break the world download record with the release of Firefox 3.<ref name="WorldRecord">{{cite web |url=http://www.spreadfirefox.com/worldrecord/ |title=Set a Guinness World Record Enjoy a Better Web |last=Colvig |first=Mary |date=July 2, 2008 |work=Mozilla Blog |publisher=Mozilla Foundation |archive-url=https://web.archive.org/web/20110112114317/http://blog.mozilla.com/blog/2008/07/02/were-official/ |archive-date=January 12, 2011 |access-date=May 30, 2008}}</ref> This resulted in an official certified [[Guinness world record]], with over eight million downloads.<ref>{{cite news |url=http://www.computerworld.com/s/article/9215243/Firefox_4_sets_unofficial_download_record |title=Firefox 4 sets unofficial download record |last=Keizer |first=Gregg |date=March 27, 2011 |work=Computerworld |access-date=August 21, 2012 |archive-url=https://web.archive.org/web/20121011112844/http://www.computerworld.com/s/article/9215243/Firefox_4_sets_unofficial_download_record |archive-date=October 11, 2012 |url-status=live}}</ref> In February 2011, Mozilla announced that it would be retiring Spread Firefox (SFX). Three months later, in May 2011, Mozilla officially closed Spread Firefox. Mozilla wrote that "there are currently plans to create a new iteration of this website [Spread Firefox] at a later date."<ref>{{cite web |last=Snyder |first=Ryan |title=Spread Firefox |publisher=Mozilla Blog |date=February 25, 2011 |url=https://blog.mozilla.org/website-archive/2011/02/25/spread-firefox/ |access-date=May 15, 2012 |archive-url=https://web.archive.org/web/20120601030624/http://blog.mozilla.org/website-archive/2011/02/25/spread-firefox/ |archive-date=June 1, 2012}}</ref>

In celebration of the third anniversary of the founding of the [[Mozilla Foundation]], the "World Firefox Day" campaign was established on July 15, 2006,<ref>{{cite web |title=World Firefox Day Launches |author=Sfx Team |publisher=Spread Firefox: Sfx Team's Blog |url=http://www.spreadfirefox.com/node/24241 |archive-url=https://web.archive.org/web/20061210145456/http://www.spreadfirefox.com/node/24241 |archive-date=December 10, 2006 |access-date=January 24, 2007 |date=July 16, 2006}}</ref><ref>{{cite web |url=https://www-archive.mozilla.org/press/mozilla-foundation.html |title=Mozilla Foundation Announcement |date=July 15, 2003 |publisher=Mozilla |access-date=June 18, 2018 |archive-url=https://web.archive.org/web/20180315101954/https://www-archive.mozilla.org/press/mozilla-foundation.html |archive-date=March 15, 2018 |url-status=live}}</ref> and ran until September 15, 2006.<ref>{{cite web |title=Friends of Firefox Frequently Asked Questions |url=http://www.worldfirefoxday.com/faq.php |archive-url=https://web.archive.org/web/20071116084027/http://worldfirefoxday.com/faq.php |archive-date=November 16, 2007 |access-date=November 27, 2007}}</ref> Participants registered themselves and a friend on the website for nomination to have their names displayed on the Firefox Friends Wall, a digital wall that was displayed at the headquarters of the Mozilla Foundation.

The Firefox community has also engaged in the promotion of its web browser. In 2006, some of Firefox's contributors from [[Oregon State University]] made a [[crop circle]] of the Firefox logo in an [[oat]] field near [[Amity, Oregon]], near the intersection of Lafayette Highway and Walnut Hill Road.<ref>{{cite web |url=http://firefoxcropcircle.com/circle/ |title=Take Back the Field |work=Oregon State Linux Users Group |date=August 14, 2006 |access-date=August 28, 2011 |archive-url=https://web.archive.org/web/20111006171912/http://firefoxcropcircle.com/circle/ |archive-date=October 6, 2011 |url-status=live}}</ref> After Firefox reached 500&nbsp;million downloads on February 21, 2008, the Firefox community celebrated by visiting [[Freerice]] to earn 500&nbsp;million grains of rice.<ref>{{cite web |url=http://blog.mozilla.com/blog/2008/02/21/500-million-firefox-downloads-complete-500-million-grains-in-progress/ |title=500&nbsp;million Firefox downloads: complete; 500 million grains: in progress |last=Colvig |first=Mary |date=February 21, 2008 |work=Mozilla Blog |publisher=Mozilla |access-date=June 24, 2009 |archive-url=https://web.archive.org/web/20110813142828/http://blog.mozilla.com/blog/2008/02/21/500-million-firefox-downloads-complete-500-million-grains-in-progress/ |archive-date=August 13, 2011 |url-status=live}}</ref>

Other initiatives included Live Chat – a service Mozilla launched in 2007 that allowed users to seek technical support from volunteers.<ref>{{cite web |url=http://blog.mozilla.com/sumo/2007/12/28/firefox-live-chat-launching-today/ |title=Firefox Support Blog " Blog Archive " Firefox Live Chat launching today |last=Tenser |first=David |date=December 28, 2007 |publisher=The Mozilla Blog |access-date=August 6, 2009 |archive-url=https://web.archive.org/web/20110827184112/http://blog.mozilla.com/sumo/2007/12/28/firefox-live-chat-launching-today/ |archive-date=August 27, 2011 |url-status=live}}</ref> The service was later retired.<ref name="Brinkmann8">{{cite news |url=https://www.ghacks.net/2008/01/02/firefox-live-chat-support/ |title=Firefox Live Chat Support |last=Brinkmann |first=Martin |date=January 2, 2008 |newspaper=gHacks Technology News |access-date=May 2, 2014 |archive-url=https://web.archive.org/web/20140502143814/http://www.ghacks.net/2008/01/02/firefox-live-chat-support/ |archive-date=May 2, 2014 |url-status=live}}</ref>

To promote the launch of Firefox Quantum in November 2017, Mozilla partnered with [[Reggie Watts]] to produce a series of TV ads and social media content.<ref>{{cite web |url=https://blog.mozilla.org/blog/2017/11/14/fast-for-good-launching-the-new-firefox-into-the-world/ |title=Mozilla Blog |date=November 14, 2017 |publisher=The Mozilla Blog |access-date=July 23, 2018 |archive-url=https://web.archive.org/web/20180723082154/https://blog.mozilla.org/blog/2017/11/14/fast-for-good-launching-the-new-firefox-into-the-world/ |archive-date=July 23, 2018 |url-status=live}}</ref>

== Performance ==
=== 2000s ===
In December 2005, ''Internet Week'' ran an article in which many readers reported high memory usage in Firefox 1.5.<ref>{{cite news |last=Finnie |first=Scot |title=Firefox 1.5: Not Ready For Prime Time? |work=InformationWeek |date=December 8, 2005 |url=http://www.informationweek.com/software/opensource/174909795 |archive-url=https://web.archive.org/web/20090624202020/http://www.informationweek.com/news/showArticle.jhtml?articleID=174909795 |archive-date=June 24, 2009 |access-date=January 24, 2007}}</ref> Mozilla developers said that the higher memory use of Firefox 1.5 was at least partially due to the new fast backwards-and-forwards (FastBack) feature.<ref>{{cite web |last=Goodger |first=Ben |author-link=Ben Goodger |title=About the Firefox 'memory leak' |work=MozllaZine weblogs |date=February 14, 2006 |url=http://weblogs.mozillazine.org/ben/archives/009749.html |archive-url=https://web.archive.org/web/20110717141231/http://weblogs.mozillazine.org/ben/archives/009749.html |archive-date=July 17, 2011 |access-date=November 17, 2007}}</ref> Other known causes of memory problems were malfunctioning extensions such as [[Google Toolbar]] and some older versions of [[AdBlock]],<ref>{{cite web |url=http://kb.mozillazine.org/?title=Problematic_extensions&oldid=30448 |title=Problematic Extensions |access-date=January 24, 2007 |date=January 19, 2007 |publisher=MozillaZine Knowledge Base |archive-url=https://web.archive.org/web/20110501042724/http://kb.mozillazine.org/?title=Problematic_extensions&oldid=30448 |archive-date=May 1, 2011 |url-status=live}}</ref> or plug-ins, such as older versions of Adobe Acrobat Reader.<ref>{{cite web |url=http://kb.mozillazine.org/?title=Adobe_Reader&oldid=30451 |title=Adobe Reader |access-date=January 24, 2007 |date=January 17, 2007 |publisher=MozillaZine Knowledge Base |archive-url=https://web.archive.org/web/20110501042720/http://kb.mozillazine.org/?title=Adobe_Reader&oldid=30451 |archive-date=May 1, 2011 |url-status=live}}</ref> When ''PC Magazine'' in 2006 compared memory usage of Firefox 2, [[Opera (web browser)|Opera 9]], and [[Internet Explorer 7]], they found that Firefox used approximately as much memory as each of the other two browsers.<ref>{{cite news |url=https://www.pcmag.com/article2/0,2817,1991370,00.asp |title=Which New Browser Is Best: Firefox 2, Internet Explorer 7, or Opera 9? |access-date=January 24, 2007 |date=July 19, 2006 |last=Muchmore |first=Michael W. |work=[[PC Magazine]] |archive-url=https://web.archive.org/web/20080317040651/http://www.pcmag.com/article2/0,2817,1991370,00.asp |archive-date=March 17, 2008 |url-status=live}}</ref>

In 2006, [[Softpedia]] noted that Firefox 1.5 took longer to start up than other browsers,<ref>{{cite web |url=http://www.softpedia.com/reviews/windows/Mozilla-Firefox-Review-13677.shtml |title=Mozilla Firefox 1.5 Final Review |access-date=September 22, 2006 |date=November 30, 2005 |last=Muradin |first=Alex |publisher=Softpedia |archive-url=https://web.archive.org/web/20061027180757/http://www.softpedia.com/reviews/windows/Mozilla-Firefox-Review-13677.shtml |archive-date=October 27, 2006 |url-status=live}}</ref> which was confirmed by further [[browser speed test|speed tests]].<ref name=speedcmp>{{cite web |url=http://www.howtocreate.co.uk/browserSpeed.html#winspeed |title=Browser Speed Comparisons |access-date=January 24, 2007 |last=Wilton-Jones |first=Mark |publisher=How To Create |archive-url=https://web.archive.org/web/20110622065856/http://www.howtocreate.co.uk/browserSpeed.html#winspeed |archive-date=June 22, 2011 |url-status=live}}</ref>

Internet Explorer 6 launched more swiftly than Firefox 1.5 on [[Windows XP]] since many of its components were built into the OS and loaded during system startup.<!--<ref name=speedcmp /> --> As a workaround for the issue, a preloader application was created that loaded components of Firefox on startup, similar to Internet Explorer.<ref>{{cite web |url=https://sourceforge.net/projects/ffpreloader/ |title=Firefox Preloader |access-date=April 26, 2007 |publisher=SourceForge |archive-url=https://web.archive.org/web/20070513224644/http://sourceforge.net/projects/ffpreloader |archive-date=May 13, 2007 |url-status=live}}</ref> A [[Windows Vista]] feature called [[Windows Vista I/O technologies#SuperFetch|SuperFetch]] performs a similar task of preloading Firefox if it is used often enough.{{Citation needed|date=September 2020}}

Tests performed by ''[[PC World]]'' and Zimbra in 2006 indicated that Firefox 2 used less memory than Internet Explorer 7.<ref name=pcworldreview>{{cite news |last=Larkin |first=Erik |title=Radically New IE 7 or Updated Mozilla Firefox 2 – Which Browser Is Better? |work=[[PC World]] |date=October 24, 2006 |url=http://www.pcworld.com/article/127309-6/radically_new_ie_7_or_updated_mozilla_firefox_2which_browser_is_better.html |access-date=May 18, 2007 |archive-url=https://web.archive.org/web/20080913021731/http://www.pcworld.com/article/127309-6/radically_new_ie_7_or_updated_mozilla_firefox_2which_browser_is_better.html |archive-date=September 13, 2008 |url-status=live}}</ref><ref>{{cite web |last=Dargahi |first=Ross |title=IE 7 vs IE 6 |publisher=Zimbra |date=October 19, 2006 |url=http://www.zimbrablog.com/blog/archives/2006/10/ie-7-vs-ie-6.html |access-date=January 24, 2007 |archive-url=https://web.archive.org/web/20080615025653/http://www.zimbrablog.com/blog/archives/2006/10/ie-7-vs-ie-6.html |archive-date=June 15, 2008 |url-status=dead}}</ref> Firefox 3 used less memory than Internet Explorer 7, Opera 9.50 Beta, [[Safari (web browser)|Safari]] 3.1 Beta, and Firefox 2 in tests performed by Mozilla, CyberNet, and The Browser World.<ref>{{cite news |first=Ryan |last=Paul |title=Firefox 3 goes on a diet, eats less memory than IE and Opera |publisher=Ars Technica |date=March 17, 2008 |url=https://arstechnica.com/open-source/news/2008/03/firefox-3-goes-on-a-diet-eats-less-memory-than-ie-and-opera.ars |access-date=June 1, 2008 |archive-url=https://web.archive.org/web/20090131231615/http://arstechnica.com/open-source/news/2008/03/firefox-3-goes-on-a-diet-eats-less-memory-than-ie-and-opera.ars |archive-date=January 31, 2009 |url-status=live}}</ref><ref>{{cite news |url=http://cybernetnews.com/cybernotes-browser-performance-comparisons/ |title=Browser Performance Comparisons |last=Ryan |first=Wagner |date=March 26, 2008 |access-date=June 1, 2008 |publisher=CyberNet News |archive-url=https://web.archive.org/web/20090625154908/http://cybernetnews.com/cybernotes-browser-performance-comparisons/ |archive-date=June 25, 2009 |url-status=live}}</ref><ref>{{cite web |title=Firefox 3.0 Beta 4 Vs Opera 9.50 Beta Vs Safari 3.1 Beta: Multiple Sites Opening Test |publisher=The Browser World |date=March 29, 2008 |url=http://www.thebrowserworld.com/2008/03/29/firefox-30-beta-4-vs-opera-950-beta-vs-safari-31-beta-multiple-sites-opening-test/ |access-date=June 1, 2008 |archive-url=https://web.archive.org/web/20080616073517/http://www.thebrowserworld.com/2008/03/29/firefox-30-beta-4-vs-opera-950-beta-vs-safari-31-beta-multiple-sites-opening-test/ |archive-date=June 16, 2008}}</ref> In mid-2009, BetaNews benchmarked Firefox 3.5 and declared that it performed "nearly ten times better on XP than Microsoft Internet Explorer 7".<ref name="betanews">{{cite news |url=http://www.betanews.com/article/The-final-score-Firefox-35-performs-at-251-the-speed-of-30/1246470925 |title=The final score: Firefox 3.5 performs at 251% the speed of 3.0 |last=Fulton, III |first=Scott M. |date=July 1, 2009 |access-date=May 4, 2010 |publisher=BetaNews |archive-url=https://web.archive.org/web/20090704025550/http://www.betanews.com/article/The-final-score-Firefox-35-performs-at-251-the-speed-of-30/1246470925 |archive-date=July 4, 2009 |url-status=live}}</ref>

Firefox's market share was increasing by a lot, gaining it mostly from Internet Explorer. It could have become the browser with the most market share if [[Google Chrome]] didn't launch around that time and steal lots of market share. Chrome is now the most used browser in the world, with almost 75% of market share.

=== 2010s ===
In January 2010, Lifehacker compared the performance of Firefox 3.5, Firefox 3.6, Google Chrome 4 (stable and Dev versions), Safari 4, and Opera (10.1 stable and 10.5 pre-alpha versions). Lifehacker timed how long browsers took to start and reach a page (both right after boot-up and after running at least once already), timed how long browsers took to load nine tabs at once, tested JavaScript speeds using Mozilla's Dromaeo online suite (which implements Apple's [[Browser speed test#Apple benchmarks|SunSpider]] and Google's V8 tests) and measured memory usage using Windows 7's process manager. They concluded that Firefox 3.5 and 3.6 were the fifth- and sixth-fastest browsers, respectively, on startup, 3.5 was third- and 3.6 was sixth-fastest to load nine tabs at once, 3.5 was sixth- and 3.6 was fifth-fastest on the JavaScript tests. They also concluded that Firefox 3.6 was the most efficient with memory usage followed by Firefox 3.5.<ref>{{cite news |url=https://lifehacker.com/5457242/browser-speed-tests-firefox-36-chrome-4-opera-105-and-extensions |title=Browser Speed Tests: Firefox 3.6, Chrome 4, Opera 10.5, and Extensions |last=Purdy |first=Kevin |date=January 26, 2010 |access-date=May 4, 2010 |publisher=Lifehacker |archive-url=https://web.archive.org/web/20100504143754/http://lifehacker.com/5457242/browser-speed-tests-firefox-36-chrome-4-opera-105-and-extensions |archive-date=May 4, 2010 |url-status=live}}</ref>

In February 2012, ''[[Tom's Hardware]]'' performance tested Chrome 17, Firefox 10, [[Internet Explorer 9]], Opera 11.61, and Safari 5.1.2 on Windows 7. ''Tom's Hardware'' summarized their tests into four categories: Performance, Efficiency, Reliability, and Conformance. In the performance category they tested [[HTML5]], [[Java (software platform)|Java]], [[JavaScript]], [[Document Object Model|DOM]], [[CSS 3]], [[Adobe Flash|Flash]], [[Silverlight]], and [[WebGL]] ([[WebGL 2]] is current as of version 51; and Java and Silverlight stop working as of version 52)—they also tested startup time and page load time. The performance tests showed that Firefox was either "acceptable" or "strong" in most categories, winning three categories (HTML5, HTML5 [[hardware acceleration]], and Java), only finishing "weak" in CSS performance. In the efficiency tests, ''Tom's Hardware'' tested memory usage and management. With this category, it was determined that Firefox was only "acceptable" at performing light memory usage, while it was "strong" at performing heavy memory usage. In the reliability category, Firefox performed a "strong" amount of proper page loads. For the final category, conformance, it was determined that Firefox had "strong" conformance for JavaScript and HTML5. So in conclusion, ''Tom's Hardware'' determined that Firefox was the best browser for Windows 7 OS, but that it only narrowly beat Google Chrome.<ref>{{cite news |url=https://www.tomshardware.com/reviews/chrome-17-firefox-10-ubuntu,3129-17.html |title=Benchmark Analysis: Windows 7 and Ubuntu 11.10 |last=Overa |first=Adam |date=February 21, 2012 |newspaper=Tom's Hardware |access-date=April 8, 2012 |archive-date=September 13, 2012 |archive-url=https://archive.today/20120913011235/http://www.tomshardware.com/reviews/chrome-17-firefox-10-ubuntu,3129-17.html |url-status=live}}</ref>

In June 2013, ''Tom's Hardware'' again performance tested Firefox 22, Chrome 27, Opera 12, and [[Internet Explorer 10]]. They found that Firefox slightly edged out the other browsers in their "performance" index, which examined wait times, JavaScript execution speed, HTML5/CSS3 rendering, and hardware acceleration performance. Firefox also scored the highest on the "non-performance" index, which measured memory efficiency, reliability, security, and standards conformance, finishing ahead of Chrome, the runner-up. ''Tom's Hardware'' concluded by declaring Firefox the "sound" winner of the performance benchmarks.<ref name="Overa13">{{cite news |url=https://www.tomshardware.com/reviews/chrome-27-firefox-21-opera-next,3534-12.html |title=Chrome 27, Firefox 22, IE10, And Opera Next, Benchmarked |last=Overa |first=Adam |date=June 30, 2013 |newspaper=Tom's Hardware |access-date=May 2, 2014 |archive-date=July 3, 2013 |archive-url=https://archive.today/20130703091630/http://www.tomshardware.com/reviews/chrome-27-firefox-21-opera-next,3534-12.html |url-status=live}}</ref>

In January 2014, a benchmark testing the memory usage of Firefox 29, Google Chrome 34, and [[Internet Explorer 11]] indicated that Firefox used the least memory when a substantial number of tabs were open.<ref name="Brinkmann14">{{cite news |url=https://www.ghacks.net/2014/01/02/chrome-34-firefox-29-internet-explorer-11-memory-use-2014/ |title=Chrome 34, Firefox 29, Internet Explorer 11: Memory Use 2014 |last=Brinkmann |first=Martin |date=January 2, 2014 |newspaper=gHacks Technology News |access-date=May 2, 2014 |archive-url=https://web.archive.org/web/20140505225706/http://www.ghacks.net/2014/01/02/chrome-34-firefox-29-internet-explorer-11-memory-use-2014/ |archive-date=May 5, 2014 |url-status=live}}</ref>

In benchmark testing in early 2015 on a "high-end" Windows machine, comparing [[Microsoft Edge Legacy|Microsoft Edge [Legacy]]], Internet Explorer, Firefox, Chrome, and Opera, Firefox achieved the highest score on three of the seven tests. Four different JavaScript performance tests gave conflicting results. Firefox surpassed all other browsers on the [[Browser speed test|Peacekeeper benchmark]], but was behind the Microsoft products when tested with SunSpider. Measured with Mozilla's Kraken, it came second place to Chrome, while on Google's [[Browser speed test#Octane|Octane]] challenge, it took third behind Chrome and Opera. Firefox took the lead with WebXPRT, which runs several typical HTML5 and JavaScript tasks. Firefox, Chrome, and Opera all achieved the highest possible score on the Oort Online test, measuring WebGL rendering speed (WebGL 2 is now current). In terms of HTML5 compatibility testing, Firefox was ranked in the middle of the group.<ref name="TekRevue-2015-04-01">{{cite web |url=https://www.tekrevue.com/spartan-benchmarks-ie-chrome-firefox-opera/ |title=Spartan Benchmarks: Spartan vs. IE, Chrome, Firefox, and Opera |last=Tanous |first=Jim |date=April 1, 2015 |website=TekRevue |access-date=January 10, 2016 |archive-url=https://web.archive.org/web/20151226174659/http://www.tekrevue.com/spartan-benchmarks-ie-chrome-firefox-opera/ |archive-date=December 26, 2015 |url-status=live}}</ref>

A similar set of benchmark tests in 2016 showed Firefox's JavaScript performance on Kraken and the newer [[Browser speed test#JetStream|Jetstream]] tests trailing slightly behind all other tested browsers except Internet Explorer (IE), which performed relatively poorly. On Octane, Firefox came ahead of IE and Safari, but again slightly behind the rest, including [[Vivaldi (web browser)|Vivaldi]] and Microsoft Edge [Legacy]. Edge [Legacy] took overall first place on the Jetstream and Octane benchmarks.<ref name="digitaltrends.com">{{cite web |url=https://www.digitaltrends.com/computing/best-browser-internet-explorer-vs-chrome-vs-firefox-vs-safari-vs-edge/ |title=Battle of the best browsers: Edge vs. Chrome vs. Firefox vs. Safari vs. Opera vs. IE |last=Coppock |first=Mark |date=May 27, 2018 |website=[[Digital Trends]] |access-date=January 10, 2016 |archive-url=https://web.archive.org/web/20160103215548/http://www.digitaltrends.com/computing/best-browser-internet-explorer-vs-chrome-vs-firefox-vs-safari-vs-edge/ |archive-date=January 3, 2016 |url-status=live}}</ref>

=== 2020s ===

In 2023, Microsoft published that it corrected a mistake in MS Windows after 5 years that slowed down programs, especially Firefox.<ref>{{cite web | url=https://www.heise.de/news/Microsoft-fixt-fuenf-Jahre-alten-Performance-Bug-in-Firefox-durch-Defender-8861436.html | title=Microsoft Defender: Firefox-Performance-Bremse nach fünf Jahren gelöst | date=April 9, 2023 }}</ref>

As of September 2025, Firefox's market share is 4.45%.

=== Firefox Quantum ===
As of the adoption of Firefox 57 and Mozilla's [[Gecko (software)#Quantum|Quantum project]] entering production browsers in November 2017, Firefox was tested to be faster than Chrome in independent JavaScript tests, and demonstrated to use less memory with many browser tabs opened.<ref>{{Cite web |url=https://www.digitaltrends.com/computing/best-browser-internet-explorer-vs-chrome-vs-firefox-vs-safari-vs-edge/ |title=Firefox Quantum vs. Chrome: Which Is Faster? |last=Murray |first=Matt |date=November 18, 2017 |website=[[Digital Trends]] |access-date=April 23, 2018 |archive-url=https://web.archive.org/web/20180517061601/https://www.digitaltrends.com/computing/best-browser-internet-explorer-vs-chrome-vs-firefox-vs-safari-vs-edge/ |archive-date=May 17, 2018 |url-status=live}}</ref><ref>{{Cite news |url=https://learningenglish.voanews.com/a/five-reasons-to-try-mozilla-firefox-quantum/4116662.html |title=5 Reasons to Try Firefox 'Quantum' Browser |last1=Lynn |first1=Bryan |date=November 15, 2017 |work=[[Voice of America]] (VOA) |access-date=October 31, 2018 |last2=Robbins |first2=Jill |archive-url=https://web.archive.org/web/20181101095453/https://learningenglish.voanews.com/a/five-reasons-to-try-mozilla-firefox-quantum/4116662.html |archive-date=November 1, 2018 |url-status=live}}</ref> ''[[TechRadar]]'' rated it as the fastest web browser in a May 2019 report.<ref>{{cite web |url=https://www.techradar.com/best/browser/ |title=The Best Browser 2019 |archive-date=July 14, 2019 |access-date=July 15, 2019 |archive-url=https://web.archive.org/web/20190714204710/https://www.techradar.com/best/browser |url-status=live}}</ref>

== Usage share ==
{{Further|Usage share of web browsers}}
[[File:StatCounter-browser-ww-yearly-2009-2025.png|thumb|upright=1.36|[[Usage share of web browsers]] according to [[StatCounter]] ]]
{{firefox usage share}}
Downloads have continued at an increasing rate since Firefox 1.0 was released, and {{as of |2009|7|31|lc=y|}} Firefox had already been downloaded over one billion times.<ref>{{cite web |url=https://www.cnet.com/news/firefox-1-billion-downloads-only-part-of-the-story/ |title=Firefox: 1 billion downloads only part of the story |last=Shankland |first=Stephen |date=July 31, 2009 |publisher=CNET News |access-date=December 19, 2009 |archive-url=https://web.archive.org/web/20140609001042/http://www.cnet.com/news/firefox-1-billion-downloads-only-part-of-the-story/ |archive-date=June 9, 2014 |url-status=live}}</ref> This number does not include downloads using software updates or those from third-party websites.<ref>{{cite web |url=http://feeds.spreadfirefox.com/downloads/firefox.xml |title=Spread Firefox: Mozilla Firefox Download Counts |access-date=February 14, 2007 |publisher=Mozilla |archive-url=https://web.archive.org/web/20050717012950/http://feeds.spreadfirefox.com/downloads/firefox.xml |archive-date=July 17, 2005}}</ref> They do not represent a user count, as one download may be installed on many machines, one person may download the software multiple times, or the software may be obtained from a third-party.{{Citation needed|date=September 2020}}

In July 2010, [[IBM]] asked all employees (about 400,000) to use Firefox as their default browser.<ref>{{cite web |url=https://www.cnet.com/news/ibm-names-firefox-its-default-browser/#! |title=IBM names Firefox its default browser |last=Shankland |first=Stephen |date=July 1, 2010 |publisher=[[CNET]] |access-date=November 21, 2013 |archive-url=https://web.archive.org/web/20140418003917/http://www.cnet.com/news/ibm-names-firefox-its-default-browser/#! |archive-date=April 18, 2014 |url-status=live}}</ref>

Firefox was the second-most used web browser until November 2011, when Google Chrome surpassed it.<ref>{{cite news |url=https://gs.statcounter.com/press/chrome-overtakes-firefox-globally-for-first-time |title=Chrome Overtakes Firefox Globally for First Time |access-date=December 17, 2017 |date=December 1, 2011 |first=Amir |last=Eggheck |publisher=StatCounter |archive-url=https://web.archive.org/web/20171214120933/http://gs.statcounter.com/press/chrome-overtakes-firefox-globally-for-first-time |archive-date=December 14, 2017 |url-status=live}}</ref> According to Mozilla, Firefox had more than 450&nbsp;million users {{as of|2012|10|lc=on}}.<ref name="At a Glance">{{cite web |url=https://blog.mozilla.org/press/ataglance/ |title=At a Glance |website=Mozilla Press Center |publisher=Mozilla |access-date=December 7, 2014 |archive-url=https://web.archive.org/web/20141204035522/http://blog.mozilla.org/press/ataglance/ |archive-date=December 4, 2014 |url-status=live}}</ref><ref>{{cite web |url=https://techcrunch.com/2010/11/18/state-of-mozilla/ |title=Mozilla: $104 Million In Revenues, 400 Million Users, Google Deal Running Through 2011 |last=Siegler |first=MG |date=November 18, 2010 |archive-url=https://web.archive.org/web/20170629022722/https://techcrunch.com/2010/11/18/state-of-mozilla/ |archive-date=June 29, 2017 |url-status=live |access-date=June 8, 2011}}</ref>

In October 2024, Firefox was the fourth-most widely used desktop browser, and it was the fourth-most popular with 2.95% of worldwide [[usage share of web browsers]] across all platforms.<ref>{{cite web |title=Browser Market Share Worldwide |url=https://gs.statcounter.com/browser-market-share#monthly-202309-202410 |website=StatCounter Global Stats |access-date=November 3, 2024 |archive-date=November 3, 2024 |archive-url=https://archive.today/20241103001910/https://gs.statcounter.com/browser-market-share%23monthly-202309-202410-bar |url-status=live }}</ref> 

{{Desktop browser usage share|firefox}}

According to the Firefox Public Data report by Mozilla, the active monthly count of Desktop clients has decreased from around 310&nbsp;million in 2017 to 200&nbsp;million in 2023.<ref>{{Cite web |title=Firefox Public Data Report |url=https://data.firefox.com/ |website=data.firefox.com |access-date=May 2, 2023 |archive-url=https://web.archive.org/web/20190504070939/https://data.firefox.com/ |archive-date=May 4, 2019 |url-status=live}}</ref>
From October 2020, the desktop market share of Firefox started to decline in countries where it used to be the most popular.
In Eritrea, it dropped from 50% in October 2020 to 9.32% in September 2021.

In Cuba, it dropped from 54.36% in Sept 2020 to 38.42% in September 2021.<ref>{{Cite web |url=https://gs.statcounter.com/browser-market-share/desktop/eritrea/ |title=Desktop Browser Market Share Eritrea |website=StatCounter Global Stats |access-date=July 12, 2020 |archive-url=https://web.archive.org/web/20190903211021/https://gs.statcounter.com/browser-market-share/desktop/eritrea#monthly-201805-201905 |archive-date=September 3, 2019 |url-status=live}}</ref><ref>{{Cite web |title=Desktop Browser Market Share Cuba |url=https://gs.statcounter.com/browser-market-share/desktop/cuba/ |website=StatCounter Global Stats |access-date=July 12, 2020 |archive-url=https://web.archive.org/web/20190903210936/https://gs.statcounter.com/browser-market-share/desktop/cuba |archive-date=September 3, 2019 |url-status=live}}</ref>

The UK<ref>{{Cite web |title=Browsers we support and why – Government Digital Service |url=https://gds.blog.gov.uk/2012/01/25/support-for-browsers/ |website=gds.blog.gov.uk |access-date=December 29, 2023 |archive-url=https://web.archive.org/web/20231229161959/https://gds.blog.gov.uk/2012/01/25/support-for-browsers/ |archive-date=December 29, 2023 |url-status=live}}</ref> and US<ref>{{Cite web |title=US Web Design System Documentation |url=https://designsystem.digital.gov/documentation/developers/ |website=U.S. Web Design System (USWDS) |access-date=December 29, 2023}}</ref> governments both follow the 2% rule. This states that only browsers with more than 2% market share among visitors of their websites will be supported. There are concerns that support for Firefox will be dropped because as of December 29, 2023, the browser market share among US government website visitors is 2.2%.<ref>{{Cite web |date=December 29, 2023 |title=analytics.usa.gov {{!}} The US government's web traffic. Analytics.usa.gov is migrating to a new web analytics platform. (Archived) |url=https://analytics.usa.gov/ |access-date=December 29, 2023 |archive-url=https://web.archive.org/web/20231229123107/https://analytics.usa.gov/ |archive-date=December 29, 2023 |url-status=live}}</ref>

{{clear}}

== Reception ==
Firefox has been criticized by web developers for late adoption of web standards and not fixing bugs which are decades old. No support for view transition, gradient and CSS features lack is also criticized.<ref>{{Cite AV media |url=https://www.youtube.com/watch?v=mmjUlFIaNLE |title=Firefox is hard to love |date=2025-02-11 |last=Theo - t3․gg |access-date=2025-02-18 |via=YouTube}}</ref> Firefox scores less on both [[HTML5test]] and JetStream2 compared to rival browsers.<ref>{{Cite news |last=Anderson |first=Tim |date=2021-06-01 |title=Firefox 89: Can this redesign stem browser's decline? |url=https://www.theregister.com/2021/06/01/firefox_89_redesign/ |access-date=2025-02-18 |work=[[The Register]]}}</ref><ref>{{Cite web |date=2024-11-24 |title=Chrome, Edge, Firefox, Opera, or Safari: Which Browser Is Best for 2025? |url=https://www.pcmag.com/picks/chrome-edge-firefox-opera-or-safari-which-browser-is-best |access-date=2025-02-18 |website=PCMAG |language=en}}</ref>

Other issues include high battery usage, being highly resource intensive,<ref>{{Cite web |author1=Marshall Honorof |date=2021-02-01 |title=Chrome vs. Firefox vs. Microsoft Edge: Which browser gobbles up the most RAM? |url=https://www.tomsguide.com/news/chrome-firefox-edge-ram-comparison |access-date=2025-02-18 |website=Tom's Guide |language=en}}</ref> removal of tab group, use of telemetry, ads in search bar, dated download system, lack of [[Progressive web app|PWA]],<ref>{{Cite news |last=Bradshaw |first=Kyle |date=2021-01-27 |title=Firefox discontinues work toward Progressive Web Apps on desktop |url=https://9to5google.com/2021/01/27/firefox-discontinues-work-pwa-desktop/ |url-status=live |archive-url=https://web.archive.org/web/20231024173757/https://9to5google.com/2021/01/27/firefox-discontinues-work-pwa-desktop/ |archive-date=2023-10-24 |work=9to5Google}}</ref> and lack of ability to share text fragment.<ref>{{Cite web |title=Firefox 131 brings tab previews, text fragment links, and security fixes |url=https://www.pcworld.com/article/2476342/firefox-131-brings-tab-previews-text-fragment-links-and-security-fixes.html |access-date=2025-02-19 |website=PCWorld |language=en}}</ref><ref>{{Cite web |last=Ahmed |first=Haamiz |date=2023-01-04 |title=10 Reasons To Stop Using Firefox |url=https://www.slashgear.com/1156016/10-reasons-to-stop-using-firefox/ |access-date=2025-02-18 |website=SlashGear |language=en-US}}</ref><!-- Firefox doesn't support native share aka Web Share API, chromecast support also missing. Find source. -->

In 2025, Mozilla introduced a [[Terms of service|terms of use]] for Firefox, as a means to give more transparency over users' rights and permissions for the browser outside of the Mozilla Public License. The company received criticism centering around a clause that gave Mozilla a "nonexclusive, royalty-free, worldwide license" to use any information that was sent to Mozilla in the process of using the browser. The new terms were perceived as privacy-compromising and were motivated by a desire to use user data in AI model training.<ref name=":4">{{Cite web |last=Perez |first=Sarah |date=2025-02-28 |title=Mozilla responds to backlash over new terms, saying it's not using people's data for AI |url=https://techcrunch.com/2025/02/28/mozilla-responds-to-backlash-over-new-terms-saying-its-not-using-peoples-data-for-ai/ |access-date=2025-09-11 |website=TechCrunch}}</ref> Mozilla denied these claims<ref>{{Cite web |last=Parrack |first=Dave |date=February 28, 2025 |title=Firefox's Updated Terms of Use Are Not As Bad As They Sound |url=https://www.makeuseof.com/mozilla-rejects-firefox-terms-of-use-claims/ |access-date=March 1, 2025 |website=MakeUseOf}}</ref><ref name=":4" /> and asserted that many modified words were to ease readability, increase transparency, formalize existing implicit agreements, and describe the circumstances of a free browser, adding that the AI features are covered by a separate agreement.<ref name=":3">{{Cite web |title=Introducing a terms of use and updated privacy notice for Firefox |url=https://blog.mozilla.org/en/products/firefox/firefox-terms-of-use/ |access-date=March 6, 2025 |website=The Mozilla Blog}}</ref><ref>{{Cite web |last=Perez |first=Sarah |date=February 28, 2025 |title=Mozilla responds to backlash over new terms, saying it's not using people's data for AI |url=https://techcrunch.com/2025/02/28/mozilla-responds-to-backlash-over-new-terms-saying-its-not-using-peoples-data-for-ai/ |access-date=March 1, 2025 |website=TechCrunch}}</ref> Criticism centered on fears that the license grant covered all data inputted, while Mozilla responded saying that the change "does NOT give us ownership of your data".<ref>{{Cite web |last=Peters |first=Jay |date=February 28, 2025 |title=Mozilla says its new Firefox terms don't give it ownership of your data |url=https://www.theverge.com/news/621796/mozilla-firefox-terms-of-use-ownership-data |access-date=March 1, 2025 |website=The Verge}}</ref><ref name=":3" /> Days later, in an attempt to respond to the fallout, Mozilla changed the wording of their privacy FAQ,<ref>{{Cite web |last=Peters |first=Jay |date=March 1, 2025 |title=Mozilla is already revising its new Firefox terms to clarify how it handles user data |url=https://www.theverge.com/news/622080/mozilla-revising-firefox-terms-of-use-data |access-date=19 March 2025 |website=The Verge}}</ref> removing a pledge to never "sell your personal data" and revising another section denying allegations that it sold user data, saying that it gathers some information from hideable advertisements as well as chatbot metadata when interacted with, and that the legal definition of "sell" was vague in some jurisdictions.<ref>{{Cite web |last=Lakshmanan |first=Ravie |date=March 1, 2025 |title=Mozilla Updates Firefox Terms Again After Backlash Over Broad Data License Language |url=https://thehackernews.com/2025/03/mozilla-updates-firefox-terms-again.html |access-date=March 1, 2025 |website=The Hacker News}}</ref><ref>{{Cite web |last=Brodkin |first=Jon |date=February 28, 2025 |title=Firefox deletes promise to never sell personal data, asks users not to panic |url=https://arstechnica.com/tech-policy/2025/02/firefox-deletes-promise-to-never-sell-personal-data-asks-users-not-to-panic/ |access-date=March 1, 2025 |website=Ars Technica}}</ref>

== See also ==
{{Portal|Internet|Linux|Free and open-source software}}
* [[Firefox User Extension Library]]
* [[History of the web browser]]
* [[List of free and open-source software packages]]
* [[Mozilla Prism]]
* [[XULRunner]]
* [[Mozilla Thunderbird]]

== References ==
{{Reflist}}

== Further reading ==
{{refbegin|30em}}
* {{cite book |last=Cheah |first=Chu Yeow |year=2005 |title=Firefox Secrets: A Need-to-Know Guide |publisher=O'Reilly |isbn=978-0-9752402-4-3 |url=https://archive.org/details/firefoxsecrets0000chea}}
* {{cite book |last=Feldt |first=Kenneth C. |year=2007 |title=Programming Firefox |publisher=O'Reilly |isbn=978-0-596-10243-2}}
* {{cite book |last=Granneman |first=Scott |year=2005 |title=Don't Click on the Blue e!: Switching to Firefox |publisher=O'Reilly |isbn=978-0-596-00939-7}}
* {{cite book |last=Hofmann |first=Chris |author2=Marcia Knous |author3=John Hedtke |year=2005 |title=Firefox and Thunderbird Garage |publisher=Prentice Hall PTR |isbn=978-0-13-187004-8}}
* {{cite book |last=McFarlane |first=Nigel |year=2005 |title=Firefox Hacks |publisher=O'Reilly |isbn=978-0-596-00928-1 |url=https://archive.org/details/firefoxhackstips00mcfa}}
* {{cite book |last=Reyes |first=Mel |year=2005 |title=Hacking Firefox: More Than 150 Hacks, Mods, and Customizations |url=https://archive.org/details/hackingfirefoxmo0000reye |url-access=registration |publisher=Wiley |isbn=978-0-7645-9650-6}}
* {{cite book |last=Ross |first=Blake |author-link=Blake Ross |year=2006 |title=Firefox for Dummies |publisher=Wiley |isbn=978-0-471-74899-1}}
{{Refend}}

== External links ==
{{Sister project links|wikt=Firefox|q=no|s=no|d=Q698|b=Using Firefox|voy=no|m=no|mw=Firefox|species=no}}
* [https://www.mozilla.org/en-US/firefox/new/ Official website]
*[https://www.microsoft.com/p/mozilla-firefox/9nzvdkpmr9rd Firefox] at [[Microsoft Store]]

{{Mozilla projects}}
{{gopher clients}}
{{Aggregators}}
{{Timeline of web browsers|2000s}}
{{Web browsers|active}}
{{Authority control}}

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