View source for Qt (software)

{{For|the company formerly known as Qt Software|Qt Group}}
{{Confuse|QuickTime}}

{{Use dmy dates|date=March 2025}}
{{Infobox software
| name = Qt (software)
| title = Qt
| logo = Qt logo neon 2022.svg
| logo size = 150px
| screenshot = Qt Creator 4 13 2 HeartRateGame.png
| collapsible = yes
| caption = GUI designing in [[Qt Creator]] using the embedded Qt Designer on [[Windows 10]]
| author = Haavard Nord and Eirik Chambe-Eng<ref name="oreilly-qt" />
| developer = {{unbulleted list|[[Trolltech]] (1991–2008)||[[Nokia]] (2008–2011)|[[Qt Project]] (2011–present)|Digia (2012–2014)||[[The Qt Company]] (2014–present)}}
| released = {{Start date and age|df=yes|1995|05|20}}<ref name="oreilly-qt" />
| latest release version = {{wikidata|property|edit|reference|P348}}
| latest release date = {{start date and age|{{wikidata|qualifier|P548=Q2804309|P348|P577}}}}
| programming language = [[C++]] ([[C++17]])
| operating system = [[Android (operating system)|Android]], [[Genode|Genode / Sculpt]], [[Haiku (operating system)|Haiku]], [[iOS]], [[Linux]] ([[Linux on embedded systems|embedded]], [[Wayland (display server protocol)|Wayland]], [[X Window System|X11]]), [[macOS]], [[Microsoft Windows]], [[WebAssembly]], [[List of platforms supported by Qt|...]]<ref>{{cite web|url=https://doc.qt.io/qt-5/supported-platforms.html|title=Supported Platforms}}</ref><!-- In Infobox reference platforms only for brevity reasons. -->
| platform = [[Cross-platform]]
| size = 
| genre = [[Cross-platform software]] and [[Software development tools]]
| license = {{Plainlist|
* [[Qt Commercial License]]<ref name="Qt Commercial Licenses"/>
* [[GNU General Public License|GPL 2.0, 3.0]]<ref name="Qt Licensing 2016"/>
* [[GNU Lesser General Public License|LGPL 3.0]]<ref name="Adding LGPLv3">{{cite web |url=https://blog.qt.io/blog/2014/08/20/adding-lgpl-v3-to-qt/ |title=Adding LGPL v3 to Qt |date=20 August 2014}}</ref>}}
| website = {{URL|https://www.qt.io}}
}}
{{Short description|Object-oriented framework for software development}}

'''Qt''' ({{IPA|/ˈkjuːt/}} pronounced "cute"<ref>{{cite web|url=https://www.qt.io/about-us/|title=Qt - About Us|archive-url=https://web.archive.org/web/20170222172844/https://www.qt.io/about-us/|archive-date=22 February 2017}}</ref><ref>{{cite web |url=http://bits.blogs.nytimes.com/2010/02/16/that-smartphone-is-so-qt/ |title=That Smartphone Is So Qt |date=16 February 2010 |author=Ashlee Vance |author-link=Ashlee Vance |access-date=19 February 2010 }}</ref>) is a cross-platform application development framework for creating [[graphical user interfaces]] as well as [[Cross-platform software|cross-platform]] applications that run on various software and hardware platforms such as [[Linux]], [[Windows]], [[macOS]], [[Android (operating system)|Android]] or [[embedded system]]s with little or no change in the underlying codebase while still being a native application with native capabilities and speed.

Qt is currently being developed by [[The Qt Company]], a publicly listed company, and the [[Qt Project]] under [[open-source governance]], involving individual developers and organizations working to advance Qt.<ref>{{cite web|url=https://dot.kde.org/2011/10/21/kde-applauds-qts-move-open-governance |title=KDE Applauds Qt's Move to Open Governance |publisher=KDE.News |first=Lydia|last=Pintscher |date=21 October 2011 |access-date=8 May 2013}}</ref><ref>{{cite news|last=Meyer |first=David |url=https://www.zdnet.com/article/nokia-gives-qt-open-source-governance/ |title=Nokia gives Qt open-source governance |work=ZDNet |date=24 October 2011 |access-date=8 May 2013}}</ref><ref>{{cite web|url=https://blog.qt.io/blog/2014/08/06/defragmenting-qt-and-uniting-our-ecosystem/|title=Defragmenting Qt and Uniting Our Ecosystem|first1=Lars|last1=Knoll|date=6 August 2014}}</ref> Qt is available under both commercial licenses<ref name="Qt Commercial Licenses" /> and [[open-source]]<ref name="Qt Licensing" /> [[GNU General Public License|GPL]] 2.0, GPL 3.0, and [[GNU Lesser General Public License|LGPL]] 3.0 licenses.<ref name="Qt Licensing 2016" /><ref name="Adding LGPLv3" />

== Purposes and abilities ==
Qt is used for developing [[graphical user interface]]s (GUIs) and multi-platform [[application software|applications]] that run on all major [[Desktop computer|desktop]] platforms and mobile or embedded platforms.
Most GUI programs created with Qt have a native-looking interface, in which case Qt is classified as a ''[[widget toolkit]]''. Non-GUI programs can also be developed, such as [[Command-line interface|command-line]] tools and consoles for servers.  An example of such a non-GUI program using Qt is the Cutelyst [[web framework]].<ref>{{cite web|url=http://cutelyst.org/ |title=Cutelyst - Home}}</ref>

Qt supports various C++ compilers, including the [[GNU Compiler Collection|GCC]] and [[Clang]] C++ compilers and the [[Microsoft Visual Studio|Visual Studio]] suite.  It supports other languages with bindings or extensions, such as [[Python (programming language)|Python]] via Python bindings<ref>{{
Cite web|date=27 December 2023|
title=PyQt Documentation|
url=https://www.riverbankcomputing.com/static/Docs/PyQt6/index.html|
website=www.riverbankcomputing.com
}}</ref> and [[PHP]] via an extension for PHP5,<ref>{{Cite web|date=10 October 2020|title=PHP-Qt - the Qt extension for php|url=http://www.php-qt.org/|url-status=live|archive-url=https://archive.today/20201012023551/http://www.php-qt.org/|archive-date=12 October 2020|access-date=12 October 2020|website=www.php-qt.org}}</ref> and has extensive [[internationalization and localization|internationalization]] support. Qt also provides [[Qt Quick]], that includes a [[Declarative programming|declarative]] [[scripting language]] called [[QML]] that allows using [[JavaScript]] to provide the logic. With Qt Quick, rapid application development for mobile devices became possible, while logic can still be written with native code as well to achieve the best possible performance.

Other features include [[SQL]] database access, [[XML]] parsing, [[JSON]] parsing, [[Thread (computing)|thread]] management and network support.

== Releases ==

The latest version of the Qt Framework is Qt 6.9, which was released on 2 April 2025.<ref>{{cite web |author1=Volker Hilsheimer |title=Qt 6.9 Released |url=https://www.qt.io/blog/qt-6.9-released |website=www.qt.io |language=en}}</ref>

Also still supported are — for commercial users — 6.5 LTS, released on 3 April 2023, 6.2 LTS,<ref>{{cite web|url=https://wiki.qt.io/Qt_6.2_Release|title=Qt 6.2.2 Released|date=1 December 2021|website=Qt|publisher=The Qt Company|access-date=6 December 2021}}</ref> released on 30 September 2021, and 5.15 LTS, released on 26 May 2020 – [[long-term support]] (LTS) versions are generally supported for three years with a commercial license, while 5.15 support was extended to five years for subscription license holders, and so it is supported until 26 May 2025. Additionally the [[KDE]] project provides unofficial support for, at least, Qt 5.15, i.e. not just for commercial users.

== Qt in use ==
In 2017, the Qt Company estimated a community of about 1 million developers worldwide<ref>{{cite web
|url=https://investors.qt.io/releases/?release=A84F7B0247145FCF
|title=QT GROUP OYJ - Managers' Transactions, 12/4/2017
|date=12 April 2017
|access-date=8 June 2017
}}</ref> in over 70 industries.<ref>{{cite book
|url=https://books.google.com/books?id=t6uQNbVYoJoC&pg=PA172
|title=Handbook of Research on Born Globals, Chapter 10: Born Global Firms, Internet, and New Forms of Internationalization
|first=Rotem
|last=Shneor
|date=2012
|publisher=Edward Elgar
|access-date=8 June 2017
|isbn=9780857938046
}}</ref>

=== Desktop UIs ===
[[File:KDE Mascot Konqi for Qt.png|thumb|KDE's mascot [[Konqi]]]]
Graphical user-interfaces and [[desktop environment]]s that utilize Qt/QML as widget toolkit:
* [[KDE Plasma]], a [[libre software|libre]] [[desktop environment]] for various computing devices<ref>{{cite web|url=https://www.kde.org/developerplatform/ |title= The KDE development platform}}</ref>
* DDE ([[Deepin]] Desktop Environment) of Linux Deepin<ref>{{cite web |url=http://news.softpedia.com/news/beautifully-crafted-deepin-15-linux-os-gets-a-release-candidate-build-gallery-498074.shtml |title=Beautifully Crafted Deepin 15 Linux OS Drops Ubuntu for Debian Sid, RC Out Now |author=Marius Nestor |date=24 December 2015 |quote=The Deepin desktop environment has been refactored in the latest Qt GUI toolkit, replacing the HTML5 and WebKit frameworks, while Go is still used for the backend.}}</ref><ref>{{cite web|url=https://www.deepin.org/2015/12/23/deepin-15-rc-make-you-only-have-eyes-for-us-by-the-sincerity/|title=深度操作系统 15 RC ——用真心捕获你的芳心 – 深度科技社区|date=23 December 2015|website=Deepin.org|access-date=15 June 2017|archive-date=17 May 2017|archive-url=https://web.archive.org/web/20170517234458/https://www.deepin.org/2015/12/23/deepin-15-rc-make-you-only-have-eyes-for-us-by-the-sincerity/|url-status=dead}}</ref>
* UKUI ([[Ubuntu Kylin]] User Interface)<ref>{{cite web|url=https://www.omgubuntu.co.uk/2020/02/ubuntu-kylin-ukui-desktop-qt|title=Wowser, the UKUI 3.0 Desktop Looks Phenomenal (Updated)|author=Joey Sneddon|website=omg!ubuntu!|date=5 February 2020 }}</ref>
* CutefishDE, a desktop environment built with Qt Quick and essential KDE frameworks <ref>{{cite web|url=https://www.omgubuntu.co.uk/2021/06/cutefish-new-linux-desktop-environment |title= OMGUbuntu Review|date= 11 June 2021}}</ref> 
* [[LXQt]] (Lightweight X11 Desktop Environment)
* [[Lumina (desktop environment)|Lumina]], a desktop environment designed for [[BSD]]-based TrueOS<ref>{{cite web|url=http://lumina-desktop.org/ |title= Lumina Homepage}}</ref>
* Lomiri (formerly [[Unity8]]),<ref>{{cite web|url=https://ubports.com/blog/ubports-blog-1/post/lomiri-new-name-same-great-unity8-265|title=Lomiri: New name, Same Great Unity8|website=ubports.com|date=12 July 2019 }}</ref> a convergent desktop environment started by Canonical, maintained by Ubports<ref>{{cite web|url=https://github.com/ubports/unity8/ |title=Unity8 Code Repository on Github|website=Github.com|date=13 September 2022 }}</ref>
* Maui Shell, a DE that also features their own app suite<ref>{{cite web|url=https://www.youtube.com/watch?v=O7gzWHJ_cW4 |title= Review by Tylers Tech channel|website= [[YouTube]]|date= 6 January 2022}}</ref>
* [[Unity (user interface)#Unity 2D|Unity 2D]], a desktop shell written in Qt and Qml
* [[Trinity Desktop Environment|Trinity DE]], a continuously developed fork based on KDE3<ref>{{cite web|url=https://www.trinitydesktop.org/about.php|title=About Trinity|website=www.trinitydesktop.org|access-date=25 April 2019}}</ref>
* [[Simple Desktop Display Manager|SDDM]], a [[X display manager|display manager]] written in [[QML]] that is compatible with [[X11]] and [[Wayland (protocol)|Wayland]].

===Embedded and mobile UIs===
* Actively developed or maintained
** [[AsteroidOS]], an open source operating system designed for smartwatches
** Avionics, Panasonic's in-flight entertainment system<ref>{{cite web|url=http://www.panasonic.aero/InflightSystems/XSeries/eXK.aspx|title=X Series Qt-based graphical user interface|access-date=14 March 2016|archive-url=https://web.archive.org/web/20160223130443/http://panasonic.aero/InflightSystems/XSeries/eXK.aspx|archive-date=23 February 2016|url-status=dead}}</ref><ref>{{cite web|url=http://www.dailymotion.com/video/x2ua0or|title=Avionics powered by Qt|date=17 June 2015 }}</ref>
** [[Sailfish OS]], a mobile operating system developed by [[Jolla]]
** [[Plasma Mobile]], a touch-based GUI developed by [[KDE]]
** [[LuneOS]], community-driven successor for Palm/HP webOS
** [[Mer (software distribution)#Nemo Mobile|Nemo Mobile]], based on Mer
** [[Lomiri]], formerly known as Unity8, a phone UI developed by Ubports, originally by Canonical
** [[Tesla Model S]] in-car UI<ref>{{cite web|url=https://www.reddit.com/r/teslamotors/comments/1p0elo/tesla_ceo_says_they_will_upgrade_model_s_browser/ccxocpn |title=Qt Interface|date=23 October 2013 }}</ref>
** [[webOS]], a multitask operating system from LG for smart devices like TVs and smartwatches
** [[Sky Q]], the home entertainment system of [[Sky plc]]<ref>{{cite web|url=http://www.digitaltveurope.net/528082/sky-teams-up-with-the-qt-company-on-sky-q-interface/ |title=Sky teams up with The QT Company on Sky Q|date=19 April 2016 }}</ref>
* Available, but inactive
** [[MeeGo]] handset and tablet UX
** [[Qtopia]], a system by Nokia for embedded and mobile devices

=== Applications using Qt ===
{{See also|Category:Software that uses Qt|Category:Proprietary software that uses Qt}}
Many notable open-source or proprietary cross-platform software are using Qt or [[QML]]: <!-- Don't list KDE applications. Almost all of them use Qt, and KDE is already mentioned under "GUI and Desktop environments". -->
{{Div col}}
* [[010 Editor]], a commercial hex editor and text editor for Microsoft Windows, Linux and macOS.
* [[Ableton Live]]
* [[Adobe Photoshop Album]]<ref>{{cite book |url=https://books.google.com/books?id=ia-smJ2_ClsC&q=Adobe+Photoshop+qt&pg=PT15 |title=C++ GUI Programming with Qt4 By Jasmin Blanchette, Mark Summerfield |isbn=9780132703000 |last1=Blanchette |first1=Jasmin |last2=Summerfield |first2=Mark |date=4 February 2008|publisher=Pearson Education }}</ref>
* [[Adobe Photoshop Elements]]<ref>{{cite book |title=Mobile Computing, Applications, and Services: First International ICST Conference, MobiCASE 2009, San Diego, CA, USA, October 26-29, 2009, Revised Selected Papers, Edited by Petros Zerfos, Rebecca Montanari, Thomas Phan |isbn=9783642126062 |last1=Zerfos |first1=Petros |last2=Montanari |first2=Rebecca |last3=Phan |first3=Thomas |date=11 May 2010 |publisher=Springer |url=https://books.google.com/books?id=RImtPKVDMG8C&q=Adobe+Photoshop+qt&pg=PA126}}</ref>
* AMD's [[Radeon Software]] Crimson Edition driver tool application.<ref>{{cite web|url=https://arstechnica.com/gaming/2015/11/amd-radeon-software-crimson-a-new-name-and-a-new-look-for-catalyst/|title=AMD Radeon Software Crimson: A new name and a new look for Catalyst|first=Mark|last=Walton|date=2 November 2015}}</ref>
* [[Audacious (software)|Audacious]], a music player for [[Linux]], Microsoft Windows, and other [[Unix-like]] operating systems.
* [[Autodesk Maya]]<ref>{{cite web |url=http://qt.nokia.com/qt-in-use/autodesk/ |title=Qt in Autodesk |url-status=dead |archive-url=https://web.archive.org/web/20110723145736/http://qt.nokia.com/qt-in-use/autodesk/ |archive-date=23 July 2011}}</ref>
* [[Autodesk 3ds Max]]<ref>{{cite web |url=https://help.autodesk.com/view/3DSMAX/2018/ENU/?guid=__developer_what_s_new_what_s_new_3ds_max_2018_sdk_html |title=What's New: 3ds Max 2018 SDK |website=help.autodesk.com |access-date=14 June 2019 |quote=3ds Max 2018 now uses Qt 5.6.2, and plug-ins can build UIs in Qt using the standard GPL Qt 5.6.2 distribution, and the Visual Studio 2015 Qt add-on}}</ref>
* [[Bitcoin Core]], the reference bitcoin implementation. Most bitcoin forks also provide the reference GUI.
* [[Calibre (software)|Calibre]], ebook collection application<ref>{{cite web |title=Plugin devs: Upcoming migration to Qt 6 - MobileRead Forums |url=https://www.mobileread.com/forums/showthread.php?t=344064}}</ref>
* [[Celestia]], real-time 3D simulator of the entire known universe (Qt only available with v1.7.0)
* [[CryEngine|CryEngine V]] editor<ref name="cryengine.com">{{cite web|url=https://www.cryengine.com/news/an-update-on-our-sandbox-interface-and-the-legacy-editor|title=An update on our Sandbox interface and the Legacy Editor}}</ref>
* [[DaVinci Resolve]], a video editor
* [[Dogecoin Core]]<ref>{{cite web | url=https://github.com/dogecoin/dogecoin | title=Dogecoin Core &#91;DOGE, Ð&#93; | website=[[GitHub]] }}</ref> community-driven cryptocurrency software.
* [[Dolphin (emulator)]], an emulator for the [[Wii]] and [[GameCube]]
* [[Dorico]] notation software
* [[Dragonframe]]<ref>{{cite web|title=Dyami Caliri, Qt Champion 2014|url=https://blog.qt.io/blog/2015/01/27/dyami-caliri-qt-champion-2014/}}</ref> stop motion animation software
* [[EAGLE (program)|EAGLE]] by [[CadSoft Computer]] / [[Autodesk]], an EDA application with schematic capture, PCB layout, auto-router and CAM features<!-- corresponding article has refs regarding Qt -->
* [[FreeCAD]], free open source parametric 3D CAD modeler
* [[FreeMat]] free open source numerical computing environment
* [[Gambas]]  free open source [[BASIC]] [[integrated development environment]]
* [[GCompris]] [[free software|free]] educational suite for children
* [[Google Earth]]<ref>{{cite web|url=http://googlesystem.blogspot.de/2010/06/google-earth-includes-web-browser.html |title=Google Earth Includes a Web Browser |publisher=Googlesystem.Blogspot.de |date=15 June 2010|access-date=8 April 2013}}</ref>
* [[GPlates]], a plate tectonics visualisation software
* [[Igor Pro]], a data analysis software
* [[Krita]] graphics editing and digital painting software<ref>{{cite web|url=https://krita.org/en/item/krita-3-0-released |title=Krita 3.0 Released |date=31 May 2016|access-date=5 September 2017}}</ref>
* [[LMMS]], a cross-platform music production software
* [[Mathematica]], a mathematical symbolic computation program, sometimes termed a computer algebra system or program, used in many scientific, engineering, mathematical, and computing fields.<ref>{{cite web |url=http://qt.digia.com/Qt-in-Action/Mathematica-by-Wolfram-Research |title=Mathematica by Wolfram Research |url-status=dead |archive-date=29 May 2013 |archive-url=https://web.archive.org/web/20130529062205/http://qt.digia.com/Qt-in-Action/Mathematica-by-Wolfram-Research}}</ref>
* [[Monero]], a privacy-focused cryptocurrency, implements its official desktop [[Cryptocurrency wallet|wallet software]] using Qt.<ref>{{cite web |title=Monero GUI |url=https://github.com/monero-project/monero-gui |website=[[GitHub]]|date=2 June 2022}}</ref>
* [[MuseScore]], an open-source, multiplatform notation software
* [[Open Broadcaster Software|OBS]], a libre cross-platform screencast software
* [[Orange (software)|Orange]] data mining suite<ref>{{cite web|url=https://github.com/biolab/orange3|title=Orange3 Data Mining Suite|website=[[GitHub]]|date=3 June 2022 }}</ref>
* [[ParaView]] open-source cross-platform application for interactive, scientific visualization<ref>{{cite web |url=https://paraview.org|title=Parallel Data Analysis and Visualization Application based on VTK}}</ref>
* [[PCSX2]], a free and open-source cross-platform Playstation 2 emulator
* [[qBittorrent]] cross-platform free and open-source BitTorrent client<ref>{{cite web|title=Qbittorrent |url=https://github.com/qbittorrent/qBittorrent |website=[[GitHub]]|date=18 February 2022}}</ref>
* [[QGIS]] geographic information system<ref>{{cite web|url=http://www.qgis.org/pyqgis-cookbook/intro.html |title=PyQGIS Developer Cookbook: Introduction |website=qgis.org |access-date=1 March 2017 |quote=the whole QGIS code depends on Qt libraries}}</ref>
* [[Qtractor]] Audio multitrack recorder and editing software
* [[QuiteRSS]] Feed Reader
* [[Retroshare]] F2F communication platform
* [[Roblox#Roblox Studio and game design|Roblox Studio]] a game creation tool used on the Roblox platform
* [[RStudio]] Desktop GUI and IDE for R statistical software<ref>{{cite book|title = Getting Started with RStudio|last = Verzani|first = John|date = 23 September 2011|publisher = O'Reilly Media, Inc|isbn = 9781449309039|page = 4}}</ref>
* [[Scribus]] desktop publishing software<ref>{{cite web|url=https://wiki.scribus.net/canvas/Development|title=Scribus Development}}</ref>
* [[Sibelius (software)|Sibelius]] music composition and notation software<ref>{{Cite web|url=http://www.sibelius.com/cgi-bin/helpcenter/chat/chat.pl?com=thread&start=702753&groupid=3&guest=1#702773|title=Sibelius - the leading music composition and notation software|website=www.sibelius.com|access-date=19 October 2016}}</ref>
* [[Soulseek|SoulseekQT]], a P2P file-sharing client<ref>{{cite web|url=http://www.slsknet.org/news/node/7|title=SoulseekQT Public Build 1|access-date=4 January 2024|archive-date=12 May 2014|archive-url=https://web.archive.org/web/20140512231731/http://www.slsknet.org/news/node/7|url-status=live}}</ref>
* [[Source 2]] engine tools<ref>{{cite web |url=https://developer.valvesoftware.com/wiki/Dota_2_Workshop_Tools/Panorama |title=Panorama |website=Valve Developer Community |access-date=28 April 2017}}</ref> a 3D video game engine developed by [[Valve Corporation|Valve]]
* [[Spyder (software)|Spyder]], a Python [[Integrated development environment|IDE]]
* [[Stellarium (software)|Stellarium]], a planetarium program
* [[Subsurface (software)|Subsurface]], a software for logging and planning scuba dives initially designed and developed by Linus Torvalds<ref>{{cite web |url=http://subsurface.hohndel.org/2013/12/subsurface-4-0-has-been-released/ |title=Subsurface 4.0 has been released |date=15 December 2013 |access-date=23 March 2016 |archive-date=12 August 2014 |archive-url=https://web.archive.org/web/20140812012445/https://subsurface.hohndel.org/2013/12/subsurface-4-0-has-been-released/ |url-status=dead }}</ref>
* [[SuperCollider]], an environment and programming language for real-time audio synthesis and algorithmic composition
* [[Synergy (software)|Synergy]], a software application for sharing a keyboard and mouse between multiple computers
* [[Teamviewer]], a computer software package for remote control, desktop sharing, online meetings, web conferencing and file transfer between computers<ref>{{cite web |url=https://community.teamviewer.com/t5/Linux/Update-TeamViewer-13/td-p/24537|title=TeamViewer 13|date=December 2017 }}</ref>
* [[Telegram (software)|Telegram]], a messaging client available for Windows, Mac and Linux<ref>{{cite web |url=https://github.com/telegramdesktop/tdesktop|title=Telegram desktop messaging app|website=[[GitHub]]|date=17 February 2022}}</ref>
* [[VirtualBox]] OS virtualization software<ref>{{cite web|url=https://www.virtualbox.org/wiki/VBoxMainLogging|title=VBoxMainLogging - Oracle VM VirtualBox}}</ref>
* [[VLC media player]]<ref>{{cite web |url=https://wiki.videolan.org/Qt_Interface/|title= Qt Interface}}</ref>
* [[WeChat]] 4.0
* [[Wireshark]], a packet analyzer<ref>{{cite web |url=https://www.wireshark.org/docs/wsdg_html_chunked/ChUIQt.html|title= Qt Application Framework}}</ref>
* [[WPS Office]]<ref>{{cite web|url=https://github.com/wps-community/wps_i18n|title=wps_i18n: KSO/WPS internationalization support|last=wps-community|date=14 June 2017|access-date=15 June 2017|via=GitHub}}</ref>
* [[XaoS]], a real-time fractal zoomer
* [[XnView MP]]<ref>{{cite web |url=http://www.xnview.com/en/xnviewmp/ |title=XnView MP}}</ref>
{{Div col end}}

=== Organizations using Qt ===
Qt is utilized by a wide range of companies and organizations such as
{{Div col|colwidth=20em}}
* [[AMD]]<ref>{{cite web | url=https://www1.qt.io/qt-news/qt-enhances-user-experience-amds-radeon-software-crimson-edition-graphic-software/ |title=AMD's Radeon Software Crimson Edition | access-date=30 June 2016}}</ref>
* [[Blizzard Entertainment]]<ref>{{cite web |url=https://github.com/blizzard/Qt |title=Blizzard's additions/modifications to Qt|website=[[GitHub]]|date=28 April 2021}}</ref>
* [[BMW]]<ref>{{cite AV media|url=https://youtube.com/watch?v=R27q5SlXVzI |archive-url=https://ghostarchive.org/varchive/youtube/20211211/R27q5SlXVzI| archive-date=11 December 2021 |url-status=live|title=QtWS16- Qt Creator as BMW Car IT Automotive IDE, Helio Chissini de Castro, BMW Car IT}}{{cbignore}}</ref>
* [[Crytek]]<ref name="cryengine.com"/>
* [[Daimler AG]]<ref>{{cite press release|url=https://www.globenewswire.com/news-release/2018/05/16/1507404/0/en/Qt-selected-for-In-Vehicle-Infotainment-IVI-Systems-by-leading-automotive-OEMs.html|title=Qt selected for In-Vehicle Infotainment (IVI) Systems by leading automotive OEMs}}</ref><ref>{{cite AV media|url=https://youtube.com/watch?v=gRYtG30yHxo |archive-url=https://ghostarchive.org/varchive/youtube/20211211/gRYtG30yHxo| archive-date=11 December 2021 |url-status=live|title=Built with Qt: Mercedes-Benz Generation EQ}}{{cbignore}}</ref>
* [[DreamWorks Pictures|DreamWorks]]<ref>{{cite AV media |url=https://www.youtube.com/watch?v=SBQGN2SfEpk |archive-url=https://ghostarchive.org/varchive/youtube/20211211/SBQGN2SfEpk| archive-date=11 December 2021 |url-status=live|title= Behind the Scenes at DreamWorks Animation: Making the Apps that Make the Movies}}{{cbignore}}</ref><ref>{{cite AV media |url=https://www.youtube.com/watch?v=2Ig_OjvPWe8 |archive-url=https://ghostarchive.org/varchive/youtube/20211211/2Ig_OjvPWe8| archive-date=11 December 2021 |url-status=live|title= UI & System Design Challenges for the NxG Lighting Tool}}{{cbignore}}</ref>
* [[Electronic Arts]]<ref>{{cite web |title=Open Source - Electronic Arts |url=http://gpl.ea.com/qtsource.html}}</ref>
* [[European Space Agency]]<ref>{{cite web |title=Qt in the European Space Agency |url=http://qt.nokia.com/qt-in-use/story/customer/esa-european-space-agency |archive-url=https://web.archive.org/web/20110723145813/http://qt.nokia.com/qt-in-use/story/customer/esa-european-space-agency |archive-date=23 July 2011 |url-status=dead}}</ref>
* [[Deutsche Flugsicherung|German Air Traffic Control]]<ref>{{cite web|url=http://conversations.nokia.com/2011/03/15/10-qt-use-cases-you-didnt-know/ | title=10 Qt use cases you didn't know |archive-url=https://web.archive.org/web/20130730003816/http://conversations.nokia.com/2011/03/15/10-qt-use-cases-you-didnt-know/ |archive-date=30 July 2013 }}</ref>
* [[HP Inc.|HP]]<ref>{{cite web |url=http://qt-project.org/videos/watch/developing_innovative_desktop_and_embedded_hp_products_with_qt |title=Developing Innovative Desktop and Embedded HP Products with Qt |archive-url=https://web.archive.org/web/20140506204024/http://qt-project.org/videos/watch/developing_innovative_desktop_and_embedded_hp_products_with_qt |archive-date=6 May 2014}}</ref>
* [[LG]]<ref>{{cite web |first=Jon |last=Porter |url=https://www.theverge.com/2019/6/26/18759414/lg-qt-partnership-webos-cars-automotive-robots-smart-home-devices |title=LG tries to bring webOS to cars, robots, and the smart home with new partnership |date=26 June 2019 |publisher=The Verge |access-date=28 April 2020}}</ref>
* [[Lucasfilm]]<ref>{{cite press release |url=https://www.businesswire.com/news/home/20071015006427/en/Lucasfilm-Ltd.-Trolltechs-Qt-Create-User-Interface#.VYJvD2RViko|title=Lucasfilm Entertainment Company Ltd.}}</ref><ref>{{cite web |url=http://qt.nokia.com/qt-in-use/qt-in-visual-effects |title=Qt in Visual Effects |url-status=dead |archive-date=23 July 2011 |archive-url=https://web.archive.org/web/20110723145754/http://qt.nokia.com/qt-in-use/qt-in-visual-effects}}</ref>
* [[Microsoft]]<ref>{{cite web |url=http://www.qtworldsummit.com/2016/sessions/how-to-transition-your-existing-native-mobile-applications-to-using-a-common-qt-based-core/ | title= Qt World Summit talk}}</ref>
* [[Panasonic]]<ref>{{cite web |url=http://qt.nokia.com/about/news/panasonic-selects-qt-for-hd-video-system |title=Panasonic selects Qt for HD video system |url-status=dead |archive-url=https://web.archive.org/web/20110723145947/http://qt.nokia.com/about/news/panasonic-selects-qt-for-hd-video-system |archive-date=23 July 2011 }}</ref>
* [[Philips]]<ref>{{cite web |url=http://qt.nokia.com/qt-in-use/qt-in-ip-communications |title=Qt in IP Communications |url-status=dead |archive-url=https://web.archive.org/web/20110723145930/http://qt.nokia.com/qt-in-use/qt-in-ip-communications |archive-date=23 July 2011 }}</ref>
* [[Robert Bosch GmbH]]<ref>{{cite web|url=https://www.qt.io/bosch-built-with-qt|title=Bosch DruckMessWT built with Qt|date=January 2019}}</ref>
* [[Samsung]]<ref>{{cite web |url=http://qt.nokia.com/qt-in-use/qt-in-home-media |title=Qt in Home Media |url-status=dead |archive-url=https://web.archive.org/web/20110723145854/http://qt.nokia.com/qt-in-use/qt-in-home-media |archive-date=23 July 2011 }}</ref>
* [[Siemens]]<ref>{{cite web |url=http://qt.nokia.com/qt-in-use/story/customer/siemens |title=Qt helped Siemens deliver a C++ development platform for manufacturing software GUIs |url-status=dead |archive-url=https://web.archive.org/web/20110714191438/http://qt.nokia.com/qt-in-use/story/customer/siemens |archive-date=14 July 2011 }}</ref>
* [[Tesla, Inc.|Tesla]]<ref>{{cite web |url=https://electrek.co/2018/05/19/tesla-releases-softwar-open-source-licences/ |title=Tesla releases some of its software to comply with open source licences |author=Fred Lambert |authorlink=Fred Lambert |date=19 May 2018}}</ref>
* [[Tomtom]]<ref>{{cite web |url=https://resources.qt.io/customer-stories-automotive/qt-testimonial-tomtom-hmi-fabrizio-monaco |title=TomTom Builds Automotive HMIs with Qt |access-date=20 May 2019 }}</ref>
* [[Valve Corporation|Valve]]<ref>{{cite web |url=https://developer.valvesoftware.com/wiki/Qt |title=Qt |website=Valve Developer Community |access-date=28 April 2017}}</ref>
* [[Volvo]]<ref>{{cite web|url=http://qt.nokia.com/qt-in-use/story/customer/volvo-mobility-systems |title=Volvo Mobility Systems |archive-url=https://web.archive.org/web/20110714191457/http://qt.nokia.com/qt-in-use/story/customer/volvo-mobility-systems |archive-date=14 July 2011 }}</ref>
* [[Walt Disney Animation Studios]]<ref>{{cite web |url=http://qt.nokia.com/qt-in-use/story/customer/walt-disney-feature-animation |title=Qt helped Walt Disney reduce development time spent on its cross-platform feature film production application |url-status=dead |archive-url=https://web.archive.org/web/20110714191507/http://qt.nokia.com/qt-in-use/story/customer/walt-disney-feature-animation |archive-date=14 July 2011 }}</ref>
{{Div col end}}

== Qt software architecture ==
[[File:Free and open-source-software display servers and UI toolkits.svg|thumb|upright=1.35|Example of Qt usage in Linux-based systems]]

=== Qt concepts ===
Qt is built on these key concepts:
;Complete abstraction of the GUI: When first released, Qt used its own paint engine and controls, emulating the look of the different platforms it runs on when it drew its widgets. This made the porting work easier because very few classes in Qt really depended on the target platform; however, this occasionally led to slight discrepancies where that emulation was imperfect. Recent versions of Qt use the native style APIs of the different platforms, on platforms that have a native widget set, to query metrics and draw most controls, and do not suffer from such issues as often.<ref>{{cite web|url=http://qt.digia.com/Product/Qt-Core-Features--Functions/Library/|title=Library|quote=Qt uses the native graphics APIs of each platform it supports, taking full advantage of system resources and ensuring that applications have native look and feel.|publisher=Digia|url-status=dead|archive-url=https://web.archive.org/web/20131101011752/http://qt.digia.com/Product/Qt-Core-Features--Functions/Library/|archive-date=1 November 2013}}</ref> On some platforms (such as MeeGo and KDE) Qt ''is'' the native API. Some other portable graphical toolkits have made different design decisions; for example, [[wxWidgets]] uses the toolkits of the target platform for its implementations.
;[[Signals and slots]]: A language construct introduced in Qt for communication between objects<ref>{{cite web|url=https://doc.qt.io/qt-5/signalsandslots.html |title=Signals & Slots - QtCore 5.1 |publisher=Qt Project |date=4 July 2013|access-date=10 April 2015}}</ref> which makes it easy to implement the [[observer pattern]] while avoiding [[boilerplate code]]. The concept is that GUI [[GUI widget|widgets]] can send signals containing event information which can be received by other controls using special functions known as slots.
;Metaobject compiler: The [[metaobject]] compiler, termed ''moc'', is a tool that is run on the sources of a Qt program. It interprets certain macros from the C++ code as annotations, and uses them to [[Automatic programming|generate added C++ code]] with meta information about the classes used in the program. This meta information is used by Qt to provide programming features not available natively in C++: signals and slots, [[Type introspection|introspection]] and asynchronous function calls.
;Language bindings:Qt can be used in several [[programming language]]s other than C++, such as Python, Javascript, C# and Rust<ref>
{{cite web|url=https://www.vandenoever.info/blog/2018/10/30/building_qt_apps_with_cargo.html|title=Qt applications with Cargo|date=30 October 2018|website=www.vandenoever.info|access-date=25 April 2019}}</ref> via [[language binding]]s; many languages have [[list of language bindings for Qt 5|bindings for Qt 5]] and [[list of language bindings for Qt 4|bindings for Qt 4]].

=== Qt modules ===
Starting with Qt 4.0 the framework was split into individual modules.<ref>{{cite web|url=https://dot.kde.org/2005/06/28/trolltech-releases-qt-40|title=Trolltech Releases Qt 4.0|publisher=[[KDE]]|date=28 June 2005|access-date=5 August 2013}}</ref><ref>{{cite web |url=https://qt-project.org/doc/qt-4.8/modules.html |title=All Modules &#124; Documentation |publisher=[[Qt Project]] |access-date=8 April 2013 |archive-url=https://web.archive.org/web/20130329130752/http://qt-project.org/doc/qt-4.8/modules.html |archive-date=29 March 2013 |url-status=dead }}</ref> With Qt 5.0 the architecture was modularized even further.<ref>{{cite web|author=Qt Blog |url=https://blog.qt.io/blog/2012/12/19/qt-5-0/ |title=Introducing Qt 5.0 &#124; Qt Blog |publisher=Digia |date=19 December 2012 |access-date=8 April 2013}}</ref><ref>{{cite web|url=https://dot.kde.org/2012/12/24/qt-50-congratulations-qt-project|title=Qt 5.0 - Congratulations to the Qt Project|author=Kyle Morris|publisher=KDE|date=24 December 2012|access-date=5 August 2013}}</ref> Qt is now split into ''essential'' and ''add-on'' modules.<ref>{{cite web|url=https://doc.qt.io/qt-6/qtmodules.html |title=Qt 6 Documentation: All Modules |publisher=Qt Project |access-date=1 December 2022}}</ref>

==== Qt essentials ====
{|class="wikitable"
|-
!style="width:12em"|Module
!Description
|-
| '''Qt Core'''
|The only required Qt module, containing classes used by other modules, including the meta-object system, concurrency and threading, containers, event system, plugins and I/O facilities.
|-
|'''Qt GUI'''
|The central GUI module. In Qt 5 this module now depends on [[OpenGL]], but no longer contains any widget classes.
|-
|'''Qt Widgets'''
|Contains classes for classic widget based GUI applications and the QSceneGraph classes. Was split off from '''QtGui''' in Qt 5.
|-
|'''Qt QML'''
|Module for [[QML]] and [[JavaScript]] languages.
|-
|'''Qt Quick'''
|The module for GUI applications written using QML2.
|-
|'''Qt Quick Controls'''
|Widget like controls for '''Qt Quick''' intended mainly for desktop applications.
|-
|'''Qt Quick Layouts'''
|Layouts for arranging items in '''Qt Quick'''.
|-
|'''Qt Network'''
|Network abstraction layer. Complete with support for [[Transmission Control Protocol|TCP]], [[User Datagram Protocol|UDP]], [[HTTP]], [[Transport Layer Security|TLS]], [[Secure Sockets Layer|SSL]] (in Qt 4) and [[SPDY]] (since Qt 5.3).
|-
|'''Qt Multimedia'''
|Classes for audio, video, radio and camera functionality.
|-
|'''Qt Multimedia Widgets'''
|The widgets from '''Qt Multimedia'''.
|-
|'''Qt SQL'''
|Contains classes for database integration using [[SQL]].
|-
|'''Qt WebEngine'''
|A new set of Qt Widget and QML webview APIs based on [[Chromium (web browser)|Chromium]].
|-
|'''Qt Test'''
|Classes for unit testing Qt applications and libraries.
|}

==== Qt add-ons ====
{|class="wikitable"
|-
!style="width:12em"|Module
!Description
|-
|'''Active Qt'''
|Classes for applications which use [[ActiveX]].
|-
|'''Qt Charts'''
|Provides functionality and widgets to plot charts of many kinds
|-
|'''Qt Bluetooth'''
|Classes accessing [[Bluetooth]] hardware.
|-
|'''Qt D-Bus'''
|Classes for IPC using the [[D-Bus]] protocol.
|-
|'''Qt NFC'''
|Classes accessing [[near-field communication|NFC]] hardware. Only officially supported on BlackBerry hardware so far (or N9 in the MeeGo port).
|-
|'''Qt OpenGL'''
|Legacy module containing the [[OpenGL]] classes from Qt 4. In Qt 5 the similar functionality in '''Qt GUI''' is recommended.
|-
|'''Qt Location'''
|Classes for accessing [[GPS]] and other location services and for mapping and navigation. Split off from the Qt 4 Mobility module of '''Qt Location'''. Supported on Android, BlackBerry, iOS, Linux (using [[GeoClue]]), Windows and Sailfish OS.
|-
|'''Qt Quick 3D'''
|Classes for rendering [[3D models]], [[video games]], simulations and [[3D user interaction|3D user interfaces]], with a '''Qt QML''' API, into a mixed 2D and 3D [[scene graph]].
|-
|'''[[QtScript|Qt Script]]'''
|Legacy module for scripting Qt application using ECMAScript/[[JavaScript]]. In Qt 5, using similar classes in '''Qt QML''' is recommended.
|-
|'''Qt Sensors'''
|Classes for accessing various mobile hardware sensors. Used to be part of Qt Mobile in Qt 4. Supported on Android, BlackBerry, iOS, WinRT, Mer and Linux.
|-
|'''Qt Serial Port'''
|Classes for access to hardware and virtual serial ports. Supported on Windows, Linux and macOS.
|-
|'''Qt WebChannel'''
|Provides access to Qt objects to HTML/Js over [[WebSocket]]s.
|-
|'''Qt WebKit'''
|Qt's [[WebKit]] implementation and API.
|-
|'''Qt WebKit Widgets'''
|The widget API for '''Qt WebKit'''
|-
|'''Qt WebSockets'''
|Provides a [[WebSocket]] implementation.
|-
|'''Qt XML'''
|Legacy module containing classes for [[Simple API for XML|SAX]] and [[Document Object Model|DOM]] style [[XML]] APIs. Replaced with QXmlStreamReader and QXmlStreamWriter classes in '''Qt Core'''.
|-
|'''Qt XML Patterns'''
|Support for [[XPath]], [[XQuery]], [[XSLT]] and [[XML Schema (W3C)|XML Schema]] validation.
|}

=== Editions ===
There are four editions of Qt available: ''Community'', ''Indie Mobile'', ''Professional'' and ''Enterprise''.<ref name = "Qt Download">{{Cite web|url = https://www.qt.io/download/|title = Qt Download page|access-date = 21 November 2014|website = Download Qt|publisher = The Qt Company}}</ref> The Community version is under the open source licenses, while the Indie Mobile, Professional and Enterprise versions, which contain additional functionality and libraries, e.g. Enterprise Controls<ref name = "Qt Download" /> are commercially sold by The Qt Company.

=== Supported platforms ===
{{Main|List of platforms supported by Qt}}

Qt works on many different platforms; the following are officially supported:

{|class="wikitable"
|-
! Platform || Description
|-
| colspan="2" style="text-align: left; background: #eaecf0;" | '''Linux/Unix'''
|-
|'''X11 '''
|Qt for [[X Window System]] ([[Linux]]<!-- Not officially(?): [[*BSD]], [[HP-UX]], [[Solaris (operating system)|Solaris]], [[AIX]], etc.-->);<ref>{{cite web|url=https://wiki.qt.io/Support_for_Linux_X11 |title=Qt Wiki&nbsp;– Support for Linux/X11 |publisher=Qt Project |date=24 March 2016 |access-date=27 July 2019}}</ref> [[FreeBSD]], [[NetBSD]], [[OpenBSD]], and [[DragonFly BSD]] have community support.
|-
|'''Wayland'''
| Qt applications can switch between graphical backends like X and [[Wayland (display server protocol)|Wayland]] at [[load time]] with the -platform command line option.<ref>{{cite web
| url = https://wiki.qt.io/Getting_Started_With_Lighthouse
| title = Getting started with Lighthouse
| access-date =25 November 2011
}}</ref><ref>{{cite web
 |url         = https://qt.gitorious.org/qt/lighthouse/commit/6c5ea196ff086b92687033208f15e36591dc70f6
 |first       = Kristian
 |last        = Høgsberg
 |date        = 25 January 2011
|title       = Add wayland lighthouse plugin
 |url-status   = dead
 |archive-url  = https://web.archive.org/web/20160203131659/https://qt.gitorious.org/qt/lighthouse/commit/6c5ea196ff086b92687033208f15e36591dc70f6
 |archive-date = 3 February 2016
}}</ref> This allows a seamless transition of Qt applications from X11 to Wayland. [[SailfishOS]] uses Wayland only as it does not have X11.<ref>{{cite web |url=https://blog.qt.io/blog/2011/03/18/multi-process-lighthouse/ |title=Multi-process Lighthouse |publisher=Qt Project|first=Jørgen|last=Lind|date=18 March 2011|access-date=21 August 2013}}</ref>
|-
|'''Android'''
|Qt for [[Android (operating system)|Android]]<ref name="Digia">{{cite web|url=https://wiki.qt.io/New-Features-in-Qt-5.1#New_Modules |title=New Features in Qt 5.1 - Support for New Platforms |publisher=Digia |date=3 July 2013 |access-date=10 April 2015}}</ref> (formerly known as Necessitas).<ref>{{cite web |url=https://necessitas.kde.org/ |title=Necessitas project |access-date=10 April 2015 |archive-url=https://web.archive.org/web/20160220103506/https://necessitas.kde.org/ |archive-date=20 February 2016 |url-status=dead }}</ref>
|-
|'''Embedded Linux'''
|Qt for embedded platforms: [[personal digital assistant]], [[smartphone]], etc.<ref>{{cite web |url=https://wiki.qt.io/Support_for_Embedded_Linux |title=Qt Wiki&nbsp;– Support for Embedded Linux |publisher=Qt Project |date=12 August 2011 |access-date=10 April 2015}}</ref> Exists as multiple platforms depending on display technology. [[DirectFB]], [[Linux framebuffer|LinuxFB]] and EGLFS ([[EGL (API)|EGL]] Full Screen).
|-
| colspan="2" style="text-align: left; background: #eaecf0;" | '''Microsoft platforms'''
|-
|'''Windows'''
|Qt for Microsoft [[Windows 7]],<ref>{{cite web|url=https://wiki.qt.io/Support_for_Windows |title=Qt Wiki&nbsp;– Support for Windows |publisher=[[Qt Project]] |date=11 August 2011 |access-date=11 August 2013}}</ref> [[Windows 8|8]] and [[Windows 10|10]]<ref>{{cite web|url=http://blog.qt.io/blog/2015/04/29/windows-10-support-in-qt/ |title=Windows 10 Support in Qt |publisher=[[The Qt Company]] |date=29 April 2015 |access-date=28 January 2016}}</ref>
|-
|'''Windows RT'''
|Support for [[Windows Runtime|WinRT]]-based [[Windows 10 Mobile]] apps and [[Windows 10 IoT]]<ref name="auto">{{cite web |url=https://doc.qt.io/qt-5/winrt-support.html|title=Qt for WinRT|publisher=[[Qt Project]]|access-date=9 September 2014}}</ref>
|-
| colspan="2" style="text-align: left; background: #eaecf0;" | '''Apple platforms'''
|-
|'''macOS'''
|Qt for Apple [[macOS]]; supports applications on [[Cocoa (API)|Cocoa]]<ref>{{cite web|url=https://wiki.qt.io/Support_for_Mac_OS_X |title=Qt Wiki&nbsp;– Support for OS X |publisher=Qt Project |date=14 August 2011 |access-date=21 August 2013}}</ref>
|-
|'''iOS'''
|Qt for [[iOS]] platforms ([[iPhone]], [[iPad]])<ref>{{cite web|url=https://doc.qt.io/qt-5/supported-platforms.html |title=Supported Platforms|access-date=1 February 2014}}</ref>
|-
| colspan="2" style="text-align: left; background: #eaecf0;" | '''Other embedded platforms'''
|-
|'''Integrity'''
|Qt for [[Integrity (operating system)|Integrity]]<ref>{{Cite web|url = https://www.qt.io/qt-framework/#section-4|title = Qt Product pages, Supported platforms|access-date = 21 November 2014|website = Qt - Product - Qt Framework|publisher = The Qt Company}}</ref>
|-
|'''QNX'''
|Qt for [[QNX]]<ref>{{cite web |author=Katherine Barrios |url=http://blog.qt.io/blog/2011/11/29/qt-commercial-formally-supports-qnx-2/ |title=Qt Commercial Formally Supports QNX &#124; Qt Blog |date=29 November 2011 |access-date=13 March 2018}}</ref><ref>{{cite web|url=http://doc.qt.io/qt-5/platform-notes-qnx.html|title=Platform and Compiler Notes - QNX {{!}} Qt 5.10}}</ref>
|-
|'''VxWorks'''
|Qt for [[VxWorks]].<ref>{{cite web |author=Tuukka Turunen |url=https://blog.qt.io/blog/2012/06/28/qt-commercial-for-vxworks-2/ |title=Qt Commercial for VxWorks &#124; Qt Blog |date=28 June 2012 |access-date=13 March 2018}}</ref><ref>{{cite web |url=https://doc.qt.io/qt-5/vxworks.html |title=Qt for VxWorks {{!}} Qt 5.10}}</ref> Only available under a [[proprietary software|proprietary]] (commercial) license. Qt 5.5.
|-
|'''QT for MCUs'''
|QT for MCUs<ref>{{cite web |url=https://doc.qt.io/QtForMCUs-2.8/ |title=Qt for MCUs 2.8.1}}</ref>
|}

After Nokia opened the Qt source code to the community on [[Gitorious]], various ports appeared. There are also some ports of Qt that may be available, but are not supported anymore. These platforms are listed in [[List of platforms supported by Qt]]. See also there for current community support for other lesser known platforms, such as [[SailfishOS]].

=== Licensing ===
Qt is available under the following free software licenses:<ref name="Qt Licensing">{{cite web |url=https://www.qt.io/faq/ |title=Legal - FAQ - Qt |publisher=The Qt Company|website=www.qt.io|access-date=25 April 2019}}</ref> [[GNU General Public License#Version 2|GPL 2.0]], [[GNU General Public License#Version 3|GPL 3.0]], [[GNU Lesser General Public License|LGPL 3.0]] and [[GNU Lesser General Public License|LGPL 2.1]] (with Qt special exception).<ref name="Qt Licensing 2016">{{cite web
|url=http://blog.qt.io/blog/2016/01/13/new-agreement-with-the-kde-free-qt-foundation/
|title= New agreement with the KDE Free Qt Foundation and changes for the open source version
|publisher= The Qt Company}}</ref><ref>{{cite web
|url=https://doc.qt.io/qt-5/lgpl.html
|title=Digia Qt LGPL Exception version 1.1}}</ref> Note that some modules are available only under a GPL license, which means that applications which link to these modules need to comply with that license.<ref>{{cite web
|url=https://www.qt.io/terms-conditions/
|publisher=[[The Qt Company]]
|access-date=7 January 2017
|title=Qt Licensing}}</ref>

In addition, Qt has always been available under a commercial license, like the Qt Commercial License,<ref name="Qt Commercial Licenses">{{cite web
|url=http://doc.qt.io/qt-5/licensing.html
|title=Licenses}}</ref> that allows developing proprietary applications with no restrictions on licensing.

=== Qt tools ===
{{See also|Qt Creator}}

Qt comes with its own set of tools to ease cross-platform development, which can otherwise be cumbersome due to different set of development tools.

[[Qt Creator]] is a cross-platform [[Integrated development environment|IDE]] for C++ and QML. [[Qt Creator#History|Qt Designer]]'s [[GUI]] layout/design functionality is integrated into the IDE, although Qt Designer can still be started as a standalone tool.

In addition to Qt Creator, Qt provides [[qmake]], a cross-platform [[Build Automation|build script generation tool]] that automates the generation of Makefiles for development projects across different platforms.
There are other tools available in Qt, including the Qt Designer interface builder and the Qt Assistant help browser (which are both embedded in Qt Creator), the Qt Linguist translation tool, uic (user interface compiler), and moc (Meta-Object Compiler).

== History of Qt ==

=== Early developments ===
In the summer of 1990, Haavard Nord and Eirik Chambe-Eng (the original developers of Qt and the CEO and President, respectively, of [[Trolltech]]) were working together on a database application for ultrasound images written in C++ and running on [[Classic Mac OS|Mac OS]], [[Unix]], and [[Microsoft Windows]].<ref name="oreilly-qt"/><ref>{{cite web|url=http://www.qt.io/qt20/|title=Qt - Qt20|work=Qt}}</ref> They began development of "Qt" in 1991, three years before the company was incorporated as Quasar Technologies, then changed the name to Troll Tech and then to Trolltech.<ref name="oreilly-qt" />

The toolkit was called Qt because the letter [[Q]] looked appealing in Haavard's [[Emacs]] typeface, and "t" was inspired by [[X Toolkit Intrinsics|Xt]], the X toolkit.<ref name="oreilly-qt">{{cite book|title=C++ GUI Programming with Qt 4 |last1=Blanchette |first1=Jasmin |last2=Summerfield |first2=Mark |publisher=[[Prentice-Hall]] |chapter=A Brief History of Qt |pages=xv–xvii |edition=1st |date=June 2006 |chapter-url=http://my.safaribooksonline.com/0131872494/pref04 |access-date=5 August 2013|archive-date=23 September 2019|archive-url=https://web.archive.org/web/20190923193951/https://my.safaribooksonline.com/0131872494/pref04}}</ref>

The first two versions of Qt had only two flavors: Qt/X11 for Unix and Qt/Windows for Windows.

On 20 May 1995 Trolltech publicly released Qt 0.90 for X11/Linux with the [[source code]] under the ''Qt Free Edition License''.<ref>{{cite web|url=https://quickgit.kde.org/?p=qt1.git&a=blob&h=2b98366d82a95f66988a7206290120e8c698ea40&f=LICENSE&o=plain |archive-url=https://web.archive.org/web/20161014010101/https://quickgit.kde.org/?p%3Dqt1.git%26a%3Dblob%26h%3D2b98366d82a95f66988a7206290120e8c698ea40%26f%3DLICENSE%26o%3Dplain|title=Qt Free Edition License |year=1992|publisher=Trolltech|access-date=14 October 2016|url-status=dead|archive-date=14 October 2016}}</ref><ref>{{cite web |url=http://blog.qt.io/blog/2015/05/20/happy-20th-anniversary-qt/|title=Happy 20th Anniversary Qt! |work=Qt Blog}}</ref><ref>{{cite web|url=http://sdtimes.com/qt-framework-celebrates-its-20th-anniversary/|title=Qt framework celebrates its 20th anniversary|work=SD Times|date=21 May 2015}}</ref> This license was viewed as not compliant with the free software definition by [[Free Software Foundation]] because, while the source was available, it did not allow the redistribution of modified versions. Trolltech used this license until version 1.45. Controversy erupted around 1998 when it became clear that the [[K Desktop Environment 1|K Desktop Environment]] was going to become one of the leading desktop environments for Linux. As it was based on Qt, many people in the [[free software movement]] worried that an essential piece of one of their major operating systems would be proprietary.

The Windows platform was available only under a proprietary license, which meant free/open source applications written in Qt for X11 could not be ported to Windows without purchasing the proprietary edition.

=== Becoming free software–friendly ===
With the release of version 2.0 of the toolkit in mid-1999, the license was changed to the [[Q Public License]] (QPL), a [[free software]] license, but one regarded by the [[Free Software Foundation]] as incompatible with the GPL. Compromises were sought between KDE and Trolltech whereby Qt would not be able to fall under a more restrictive license than the QPL, even if Trolltech was bought out or went bankrupt. This led to the creation of the KDE Free Qt foundation,<ref>{{cite web |url=https://www.kde.org/community/whatiskde/kdefreeqtfoundation.php|title=KDE Free Qt Foundation}}</ref> which guarantees that Qt would fall under a [[BSD-style license]] should no free/open source version of Qt be released during 12 months.<ref>{{cite web |url=https://www.kde.org/community/whatiskde/kdefreeqt_announcement.php|title=KDE Free Qt Foundation announcement|date=June 1998}}</ref><ref>{{cite web|url=https://www.kde.org/community/whatiskde/Software_License_agreement_2013.pdf|title=Software License Agreement|date=13 April 2013|publisher=Digia}}</ref>

In 2000, Qt/X11 2.2 was released under the GPL v2,<ref>{{cite web|url=http://qt.nokia.com/about/news/archive/00000043 |title=Trolltech offers a choice in licensing with the addition of GPL licensing for the upcoming release of Qt |publisher=Qt.nokia.com |archive-url=https://web.archive.org/web/20120313182431/http://qt.nokia.com/about/news/archive/00000043 |archive-date=13 March 2012|access-date=13 November 2011}}</ref> ending all controversy regarding [[License compatibility|GPL compatibility]].

At the end of 2001, Trolltech released Qt 3.0, which added support for Mac OS X (now known as [[macOS]]). The Mac OS X support was available only in the proprietary license until June 2003, when Trolltech released Qt 3.2 with Mac OS X support available under the GPL.

In 2002, members of the [[KDE on Cygwin]] project began porting the GPL licensed Qt/X11 code base to Windows.<ref>{{cite web |url=http://qtwin.sourceforge.net/qt3-win32/history.php|title=Q../Windows Edition history|date=5 June 2006|archive-url=https://web.archive.org/web/20100731070812/http://qtwin.sourceforge.net/qt3-win32/history.php|archive-date=31 July 2010}}</ref> This was in response to Trolltech's refusal to license Qt/Windows under the GPL on the grounds that Windows was not a free/open source software platform.<ref>[https://marc.info/?l=kde-cygwin&m=104431728920022&w=2 E-mail to the kde-cygwin mailing list] by Chris January, 4 February 2003
</ref><ref>{{cite web |url=http://www.trolltech.com/developer/faqs/noncomm.html |title=Qt Non-commercial FAQ |publisher=Trolltech |archive-url=https://web.archive.org/web/20031005175911/http://www.trolltech.com/developer/faqs/noncomm.html |archive-date=5 October 2003}}</ref> The project achieved reasonable success although it never reached production quality.

This was resolved when Trolltech released Qt 4.0 also for Windows under the GPL in June 2005.<ref>{{cite web |url=https://dot.kde.org/2005/06/28/trolltech-releases-qt-40 |title=Trolltech Releases Qt 4.0 &#124; KDE.news |date=28 June 2005 |publisher=KDE.News |access-date=13 November 2011}}</ref> Qt&nbsp;4 supported the same set of platforms in the free software/open source editions as in the proprietary edition, so it is possible, with Qt 4.0 and later releases, to create GPL-licensed free/open source applications using Qt on all supported platforms. The GPL v3 with special exception<ref>{{cite web |url=http://doc.trolltech.com/4.4/license-gpl-exceptions.html |title=Nokia Corporation Qt GPL Exception Version 1.3 |publisher=Doc.trolltech.com |date=22 July 1999 |access-date=13 November 2011 |archive-url=https://web.archive.org/web/20101003074912/http://doc.trolltech.com/4.4/license-gpl-exceptions.html |archive-date=3 October 2010 |url-status=dead }}</ref> was later added as an added licensing option. The GPL exception allows the final application to be licensed under various GPL-incompatible [[free software license|free software]]/[[open source license|open source]] licenses such as the [[Mozilla Public License]] 1.1.

=== Acquisition by Nokia ===
[[Nokia]] acquired Trolltech ASA on 17 June 2008 and changed the name first to Qt Software, then to Qt Development Frameworks.

Nokia focused on turning Qt into the main development platform for its devices, including a port to the [[Symbian]] [[S60 (software platform)|S60 platform]]. Version 1.0 of the Nokia Qt SDK was released on 23 June 2010.<ref>{{cite web|first=Niels|last=Weber |url=https://blog.qt.io/blog/2010/06/23/nokia-qt-sdk-10-released/ |title=Nokia Qt SDK 1.0 released |publisher=Labs.trolltech.com |date=23 June 2010 |access-date=13 November 2011}}</ref> The source code was made available over Gitorious, a community oriented [[Git (software)|git]] source code repository, with a goal of creating a broader community using and improving Qt.

On 14 January 2009, Qt version 4.5 added another option, the [[LGPL]],<ref>{{cite web|first=Sebastian|last=Nyström |url=https://blog.qt.io/blog/2009/01/14/nokia-to-license-qt-under-lgpl/|title=Nokia to license Qt under LGPL|date=14 January 2009 |access-date=17 September 2013}}</ref> to make Qt more attractive for both non-GPL open source projects and closed applications.<ref>{{cite web |url=https://www.ics.com/files/docs/Qt_LGPL.pdf |title=ICS Whitepaper on the Implications of Qt under LGPL for Commercial and Government users |access-date=13 November 2011}}</ref>

In February 2011, Nokia announced its decision to drop Symbian technologies and base their future smartphones on the [[Windows Phone]] platform instead (and since then support for that platform has also been dropped).<ref name="MSNokiaPressRelease2011">
{{cite press release |title= Nokia and Microsoft Announce Plans for a Broad Strategic Partnership to Build a New Global Mobile Ecosystem |url= http://www.microsoft.com/presspass/press/2011/feb11/02-11partnership.mspx |publisher= [[Microsoft]] |date= 10 February 2011 |access-date= 27 October 2011|archive-date= 1 April 2011|archive-url=https://web.archive.org/web/20110401153916/http://www.microsoft.com/presspass/press/2011/feb11/02-11partnership.mspx}}</ref> One month later, Nokia announced the sale of Qt's commercial licensing and professional services to Digia, with the immediate goal of taking Qt support to [[Android (operating system)|Android]], [[iOS]] and [[Windows 8]] platforms, and to continue focusing on desktop and embedded development, although Nokia was to remain the main development force behind the framework at that time.

=== Merging and demerging with Digia ===
In March 2011, Nokia sold the commercial licensing part of Qt to Digia, creating Qt Commercial.<ref name="Nokia and Digia">{{cite web |url=https://blog.qt.io/blog/2011/03/07/nokia-and-digia-working-together/ |title=Nokia and Digia working together to grow the Qt community |date=7 March 2011 |access-date=8 July 2011 |first=Sebastian |last=Nystrom}}</ref> In August 2012, Digia announced that it would acquire Qt from Nokia.<ref>{{cite web|author=Digia Plc |url=https://www.digia.com/en/Home/Company/Press/2012/Digia-to-acquire-Qt-from-Nokia/ |title=Digia to acquire Qt from Nokia |publisher=Digia Plc |date=9 August 2012 |access-date=17 October 2014}}</ref> The Qt team at Digia started their work in September 2012.<ref>{{cite web|author=Digia Plc |url=https://www.digia.com/en/Home/Company/Press/2012/Digia-to-acquire-Qt-from-Nokia/ |title=The journey starts today |publisher=Digia Plc |date=18 September 2012 |access-date=17 October 2014}}</ref> They released Qt 5.0 within a month and newer versions every six months with new features and additional supported platforms.

In September 2014, Digia transferred the Qt business and copyrights to their wholly owned subsidiary, The Qt Company, which owns 25 brands<ref>{{cite web|url=https://www.tmdn.org/tmview/bookmark?q=anm:%22qt%20company%22|title=TMview search result shown on September 12th, 2016|website=TMDN.org|access-date=15 June 2017}}</ref> related to Qt. In May 2016, Digia and Qt demerged completely into two independent companies.<ref>{{cite web|url=http://www.digia.com/en/actual/news/2016/digia-and-qt-have-demerged-into-two-companies--digias-new-strategys-main-themes-revealed/|title=Digia and Qt have demerged into two companies – Digia's new strategy's main themes revealed|website=Digia|access-date=15 June 2017|archive-date=17 June 2017|archive-url=https://web.archive.org/web/20170617092521/http://www.digia.com/en/actual/news/2016/digia-and-qt-have-demerged-into-two-companies--digias-new-strategys-main-themes-revealed/|url-status=dead}}</ref>

=== The Qt Project and open governance ===
{{Main|Qt Project}}

Qt 5 was officially released on 19 December 2012. This new version marked a major change in the platform, with hardware-accelerated graphics, [[QML]] and [[JavaScript]] playing a major role. The traditional C++-only QWidgets continued to be supported, but did not benefit from the performance improvements available through the new architecture.<ref>{{cite mailing list|url=https://www.mail-archive.com/qt5-feedback@qt.nokia.com/msg01420.html|title=Concern about removal of QWidget classes|mailing-list=Qt5-feedback|date=7 October 2011}}</ref> Qt 5 brings significant improvements to the speed and ease of developing user interfaces.<ref>{{cite web |url=https://blog.qt.io/blog/2011/05/09/thoughts-about-qt-5/ |title=Thoughts about Qt 5 |access-date=9 May 2011 |first=Lars |last=Knoll|publisher=Digia|date=9 May 2011}}</ref>

Framework development of Qt 5 moved to open governance at qt-project.org, which made it possible for developers outside Digia to submit patches for review.<ref>{{cite web|url=https://blog.qt.io/blog/2011/10/21/the-qt-project-is-live/|title=The Qt Project is live!|first=Lars|last=Knoll|publisher=[[Nokia]]|date=21 October 2011|access-date=8 February 2012}}</ref>

=== Qt contributors ===
[[File:Qt contributors 2013W18 without Digia.png|thumb|upright=1.35|Distribution of non-Digia Qt contributors (2013, Week 18)]]
Aside from The Qt Company, many organizations and individuals using Qt as their development platform participate in the open development of Qt via the Qt Project.<ref name="Stats2012">{{cite web|last=Macieira |first=Thiago |url=http://www.macieira.org/blog/2012/04/qt-project-statistics/ |title=Qt Project Statistics | work=Thiago Macieira's blog |publisher=Macieira.org |access-date=8 May 2013}}</ref>

One such Qt contributor is Klarälvdalens Datakonsult AB, a Swedish Qt consulting company.<ref>{{cite web |url=http://www.kdab.com/kdab-contributions-to-qt-5-0-part-1/ |title=contributions to Qt 5.0 (part 1) |publisher=KDAB |date=20 December 2012 |access-date=8 May 2013}}</ref> KDAB is involved in many areas, including maintenance of several components.<ref>{{cite web|url=http://www.kdab.com/kdab-contributions-to-qt-5-0-part-2/ |title=contributions to Qt 5.0 (part 2) |publisher=KDAB |date=21 December 2012 |access-date=8 May 2013}}</ref><ref>{{cite web|url=http://www.kdab.com/maintaining-qt3d/ |title=Maintaining Qt3D |publisher=KDAB |date=21 December 2012 |access-date=8 May 2013}}</ref>

Together with [[BlackBerry (company)|RIM/BlackBerry]], KDAB is maintaining the [[QNX]] and [[BlackBerry 10]] ports of Qt.<ref name="Stats2012" /><ref>{{cite web |url=http://www.kdab.com/qt5-on-the-qnx-operating-system/ |title=Qt5 on the QNX operating system |publisher=KDAB |date=19 April 2012 |access-date=8 May 2013}}</ref>

Another participator is [[Intel]], contributing for example [[Wayland (display server protocol)|Wayland]] support.<ref>{{cite web|url=https://www.phoronix.com/scan.php?page=news_item&px=ODYyNQ |title=[Phoronix&#93; Qt Is Now Drawing On Wayland |publisher=Phoronix.com |date=21 September 2010 |access-date=8 May 2013}}</ref> [[AudioCodes]]  maintains [[IBM Rational ClearCase|IBM ClearCase]] support in [[Qt Creator]].<ref>{{cite web|url=http://wiki.qt.io/Maintainers |title=Maintainers &#124; Qt Wiki |publisher=Qt Project |date=12 April 2013 |access-date=8 May 2013}}</ref>

As a heavy user of Qt, the [[KDE]] project submits many patches and features from its developer library [[KDE Frameworks]] back to Qt.<ref>{{cite web|url=http://community.kde.org/Frameworks/Epics/Contributions_to_Qt5|title=Frameworks/Epics/Contributions to Qt5|publisher=KDE Community Wiki|access-date=27 April 2015}}</ref>

== See also ==
* [[List of widget toolkits]]
* [[Android software development]]
* [[iOS SDK]]
* [[Wt (web toolkit)]]

== Bibliography ==
Qt Wiki provides a comprehensive list of English books about Qt.<ref>{{cite web|url=http://wiki.qt.io/Books|title=Books - Qt Wiki|website=wiki.Qt.io|access-date=15 June 2017}}</ref> This is a list of notable books:

{{Refbegin}}
* {{cite web
 |last1   = Bocklage-Ryannel
 |first1  = Juergen
 |last2   = Thelin
 |first2  = Johan
 |title   = Qt 5 Cadaques
 |edition = 1st
 |date    = 12 May 2015
|url     = https://qmlbook.github.io/
}}
* {{cite book
 |last1     = Blanchette
 |first1    = Jasmin
 |last2     = Summerfield
 |first2    = Mark
 |title     = C++ GUI Programming with Qt 4
 |edition   = 2nd
 |date      = 14 February 2008
|publisher = [[Prentice Hall]]
 |isbn      = 978-0-13-235416-5
 |url       = https://www.informit.com/store/c-plus-plus-gui-programming-with-qt4-9780132354165
}}
* {{cite book
 |last      = Summerfield
 |first     = Mark
 |title     = Advanced Qt Programming: Creating Great Software with C++ and Qt 4
 |edition   = 1st
 |date      = 23 August 2010
|publisher = [[Addison-Wesley]]
 |isbn      = 978-0-321-63590-7
 |url       = http://www.qtrac.eu/aqpbook.html
}}
* {{cite book
 |last1        = Fitzek
 |first1       = Frank H. P.
 |last2        = Mikkonen
 |first2       = Tommi
 |last3        = Torp
 |first3       = Tony
 |title        = Qt for Symbian
 |edition      = 1st
 |date         = 17 May 2010
|publisher    = [[John Wiley & Sons|Wiley]]
 |isbn         = 978-0-470-75010-0
 |url          = http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470750103.html
 |url-status   = dead
 |archive-url  = https://web.archive.org/web/20091219194350/http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470750103.html
 |archive-date = 19 December 2009
}}
* {{cite book
 |last      = Summerfield
 |first     = Mark
 |title     = Rapid GUI Programming with Python and Qt
 |edition   = 1st
 |date      = 28 October 2007
|publisher = [[Prentice Hall]]
 |isbn      = 978-0-13-235418-9
 |url       = http://www.qtrac.eu/pyqtbook.html
}}
* {{cite book
 |last         = Molkentin
 |first        = Daniel
 |title        = The Book of Qt 4: The Art of Building Qt Applications
 |edition      = 1st
 |date         = 19 July 2007
|publisher    = [[No Starch Press]]
 |isbn         = 978-1-59327-147-3
 |url          = https://www.nostarch.com/qt4.htm
 |access-date  = 18 June 2015
|archive-date = 26 June 2015
|archive-url  = https://web.archive.org/web/20150626074129/http://www.nostarch.com/qt4.htm
 |url-status   = dead
}}
* {{cite book
 |last         = Thelin
 |first        = Johan
 |title        = Foundations of Qt Development
 |edition      = 1st
 |date         = 3 August 2007
|publisher    = [[Apress]]
 |isbn         = 978-1-59059-831-3
 |url          = https://www.apress.com/9781590598313/
 |access-date  = 18 June 2015
|archive-url  = https://web.archive.org/web/20150120021243/http://www.apress.com/9781590598313
 |archive-date = 20 January 2015
|url-status   = dead
}}
* {{cite book
 |last       = Dalheimer
 |first      = Matthias
 |title      = Programming with Qt
 |edition    = 2nd
 |date       = January 2002
 |publisher  = [[O'Reilly Media]]
 |isbn       = 978-0-596-00064-6
 |url        = https://archive.org/details/programmingwithq00dalh
 |url-access = registration
}}
* {{cite book
 |last1     = Ezust
 |first1    = Alan
 |last2     = Ezust
 |first2    = Paul
 |title     = An Introduction to Design Patterns in C++ with Qt 4
 |edition   = 2nd
 |date      = 10 September 2006
|publisher = [[Prentice Hall]]
 |isbn      = 978-0-13-187905-8
 |url       = https://www.ics.com/design-patterns
}}
{{Refend}}

== References ==
{{reflist}}

== External links ==
{{Commons category|Qt}}
{{Wikibooks|Qt}}
* {{official website}}
* {{cite web |url=https://www.youtube.com/watch?v=NbTEVbQLC8s  |archive-url=https://ghostarchive.org/varchive/youtube/20211211/NbTEVbQLC8s| archive-date=11 December 2021 |url-status=live|title=The Qt 4 Dance |website=[[YouTube]]|date=11 August 2006 |format=video |access-date=7 September 2015 }}{{cbignore}}

{{Qt}}
{{KDE}}
{{Widget toolkits}}
{{GUI builders}}

[[Category:Qt (software)| ]]
[[Category:1995 software]]
[[Category:Application programming interfaces]]
[[Category:Articles with example C++ code]]
[[Category:C++ libraries]]
[[Category:Cross-platform software]]
[[Category:Cross-platform desktop-apps development]]
[[Category:Formerly proprietary software]]
[[Category:Free computer libraries]]
[[Category:Free software programmed in C++]]
[[Category:KDE]]
[[Category:Software using the GNU Lesser General Public License]]
[[Category:Widget toolkits]]
[[Category:X-based libraries]]