View source for Search engine

{{pp|small=yes}}
{{short description|Software system for finding relevant information on the Web}}
{{About|searching the World Wide Web}}{{Tone|date=June 2025}}
{{Use dmy dates|date=December 2024}}
[[File:A screenshot of suggestions by Google Search when "wikip" is typed (new).png|thumb|Some engines [[Search suggest drop-down list|suggest]] [[web query|queries]] when the user is typing in the [[search box]].]]
A '''search engine''' is a [[software system]] that provides [[hyperlink]]s to [[web page]]s, and other relevant information on [[World Wide Web|the Web]] in response to a user's [[web query|query]]. The user enters a query in a [[web browser]] or a [[mobile app]], and the [[search engine results page|search results]] are typically presented as a list of hyperlinks accompanied by textual summaries and images. Users also have the option of limiting a search to specific types of results, such as images, videos, or news.

For a search provider, its [[software engine|engine]] is part of a [[distributed computing]] system that can encompass many [[data center]]s throughout the world. The speed and accuracy of an engine's response to a query are based on a complex system of [[Search engine indexing|indexing]] that is continuously updated by automated [[web crawler]]s. This can include [[data mining]] the [[Computer file|files]] and [[database]]s stored on [[web server]]s, although some content is [[deep web|not accessible]] to crawlers.

There have been many search engines since the dawn of the Web in the 1990s, however, [[Google Search]] became the dominant one in the 2000s and has remained so. As of May 2025, according to StatCounter, Google holds approximately 89–90 % of the worldwide search share, with competitors trailing far behind: [[Microsoft Bing|Bing]] (~4 %), [[Yandex Search|Yandex]] (~2.5 %), [[Yahoo]]! (~1.3 %), [[DuckDuckGo]] (~0.8 %), and [[Baidu]] (~0.7 %).<ref name="StatCounterMay2025">StatCounter Global Stats – [https://gs.statcounter.com/search-engine-market-share Search Engine Market Share] (May 2025)</ref> Notably, this marks the first time in over a decade that Google's share has fallen below the 90 % threshold. The business of [[website]]s improving their visibility in [[search results]], known as [[search engine marketing|marketing]] and [[search engine optimization|optimization]], has thus largely focused on Google.

== History ==
{{further|Timeline of web search engines}}
<!-- Keep this list limited to notable engines (i.e., those that already have Wikipedia articles) to avoid link spam -->
{| class="wikitable sortable" style="margin-left:1em; float:right; width:25em"
|+ Timeline ([[List of search engines|full list]]) <!--Note: "Launch" refers only to web availability of original crawl-based web search engine results.-->
|-
! scope="col" | Year
! scope="col" | Engine
! style="width: 13em;" scope="col" | Current status
|-
|rowspan="4" |1993
|[[W3Catalog]]
|{{Site inactive}}
|-
|[[ALIWEB]]
|{{Site inactive}}
|-
|[[JumpStation]]
|{{Site inactive}}
|-
|[[World-Wide Web Worm|WWW Worm]]
|{{Site inactive}}
|-
| rowspan="4" |1994
|[[WebCrawler]]
|{{Site active}}
|-
|[[Go.com]]
|{{Site inactive}}, redirects to Disney
|-
|[[Lycos]]
|{{Site active}}
|-
|[[Infoseek]]
|{{Site inactive}}, redirects to Disney
|-
| rowspan="8" |1995
|[[Yahoo! Search]]
|{{Site active}}, initially a search function for [[Yahoo! Directory]]
|-
|[[Daum (web portal)|Daum]]
|{{Site active}}
|-
|[[Search.ch]]
|{{Site active}}
|-
|[[Magellan (search engine)|Magellan]]
|{{Site inactive}}
|-
|[[Excite (web portal)|Excite]]
|{{Site active}}
|-
|[[MetaCrawler]]
|{{Site active}}
|-
|[[AltaVista]]
|{{Site inactive}}, acquired by Yahoo! in 2003, since 2013 redirects to Yahoo!
|-
|[[SAPO (company)|SAPO]]
|{{Site active}}
|-
|rowspan="4" |1996
|[[RankDex]]
|{{Site inactive}}, incorporated into [[Baidu]] in 2000
|-
|[[Dogpile]]
|{{Site active}}
|-
|[[HotBot]]
|{{Site inactive}} (used [[Inktomi (company)|Inktomi]] search technology)
|-
|[[Ask.com|Ask Jeeves]]
|{{Site active}} (rebranded ask.com)
|-
| rowspan="4" |1997
|AOL NetFind
|{{Site active}} (rebranded [[AOL Search]] since 1999)
|-
|[[goo.ne.jp]]
|{{Site active}}
|-
|[[Northern Light Group|Northern Light]]
|{{Site inactive}}
|-
|[[Yandex]]
|{{Site active}}
|-
| rowspan="4" |1998
|[[Google Search|Google]]
|{{Site active}}
|-
|[[Ixquick]]
|{{Site active}} as Startpage.com
|-
|[[MSN Search]]
|{{Site active}} as Bing
|-
|[[empas]]
|{{Site inactive}} (merged with NATE)
|-
| rowspan="4" |1999
|[[AlltheWeb]]
|{{Site inactive}} (URL redirected to Yahoo!)
|-
|[[GenieKnows]]
|{{Site inactive}}, rebranded Yellowee (was redirecting to justlocalbusiness.com)
|-
|[[Naver]]
|{{Site active}}
|-
|[[Teoma]]
|{{Site inactive}} (redirect to Ask.com)
|-
| rowspan="3" |2000
|[[Baidu]]
|{{Site active}}
|-
|[[Exalead]]
|{{Site inactive}}
|-
|[[Gigablast]]
|{{Site inactive}}
|-
||2001
|[[Kartoo]]
|{{Site inactive}}
|-
| rowspan="1" |2003
|[[Info.com]]
|{{Site active}}
|-
| rowspan="4" |2004
|[[A9.com]]
|{{Site inactive}}
|-
|[[Yippy|Clusty]]
|{{Site inactive}} (redirect to DuckDuckGo)
|-
|[[Mojeek]]
|{{Site active}}
|-
|[[Sogou.com|Sogou]]
|{{Site active}}
|-
|rowspan="2" |2005
|[[SearchMe]]
|{{Site inactive}}
|-
|[[KidzSearch]]
|{{Site active}}, Google Search
|-
| rowspan="6" |2006
|[[Soso (search engine)|Soso]]
|{{Site inactive}}, merged with [[Sogou]]
|-
|[[Quaero]]
|{{Site inactive}}
|-
|[[Search.com]]
|{{Site active}}
|-
|[[ChaCha (search engine)|ChaCha]]
|{{Site inactive}}
|-
|[[Ask.com]]
|{{Site active}}
|-
|[[Live Search]]
|{{Site active}} as Bing, rebranded MSN Search
|-
| rowspan="4" |2007
|[[wikiseek]]
|{{Site inactive}}
|-
|[[Sproose]]
|{{Site inactive}}
|-
|[[Wikia Search]]
|{{Site inactive}}
|-
|[[Blackle.com]]
|{{Site active}}, Google Search
|-
| rowspan="8" |2008
|[[Powerset (company)|Powerset]]
|{{Site inactive}} (redirects to Bing)
|-
|[[Picollator]]
|{{Site inactive}}
|-
|[[Viewzi]]
|{{Site inactive}}
|-
|[[Boogami]]
|{{Site inactive}}
|-
|[[LeapFish]]
|{{Site inactive}}
|-
|[[Forestle]]
|{{Site inactive}} (redirects to Ecosia)
|-
|[[DuckDuckGo]]
|{{Site active}}
|-
|[[TinEye]]
|{{Site active}}
|-
| rowspan="6" |2009
|[[Bing (search engine)|Bing]]
|{{Site active}}, rebranded Live Search
|-
|[[Yebol]]
|{{Site inactive}}
|-
|[[Goby Inc.|Scout (Goby)]]
|{{Site active}}
|-
|[[Nate (web portal)|NATE]]
|{{Site active}}
|-
|[[Ecosia]]
|{{Site active}}
|-
|[[Startpage.com]]
|{{Site active}}, sister engine of Ixquick
|-
| rowspan="4" |2010
|[[Blekko]]
|{{Site inactive}}, sold to IBM
|-
|[[Cuil]]
|{{Site inactive}}
|-
|[[Yandex]] (English)
|{{Site active}}
|-
|[[Parsijoo]]
|{{Site active}}
|-
||2011
|[[YaCy]]
|{{Site active}}, [[Peer-to-peer|P2P]]
|-
||2012
|[[Volunia]]
|{{Site inactive}}
|-
||2013
|[[Qwant]]
|{{Site active}}
|-
| rowspan="3" |2014
|[[Egerin]]
|{{Site active}}, Kurdish / Sorani
|-
|[[Swisscows]]
|{{Site active}}
|-
|[[Searx]]
|{{Site active}}
|-
| rowspan="2" |2015
|[[Yooz]]
|{{Site inactive}}
|-
|[[Cliqz]]
|{{Site inactive}}
|-
||2016
|[[Kiddle (search engine)|Kiddle]]
|{{Site active}}, Google Search
|-
|2017
|[[Presearch (search engine)|Presearch]]
|{{Site active}}
|-
|2018
|[[Kagi (search engine)|Kagi]]
|{{Site active}}
|-
|2020
|[[Petal Search|Petal]]
|{{Site active}}
|-
| rowspan="3" |2021
|[[Brave Search]]
|{{Site active}}
|-
|Queye
|{{Site active}}
|-
|[[You.com]]
|{{Site active}}
|}

===Pre-1990s===
In 1945, [[Vannevar Bush]] described an information retrieval system that would allow a user to access a great expanse of information, all at a single desk, which he called a [[memex]].<ref>{{Cite web |last=Bush |first=Vannevar |date=1945-07-01 |title=As We May Think |url=https://www.theatlantic.com/magazine/archive/1945/07/as-we-may-think/303881/ |access-date=2024-02-22 |website=The Atlantic |language=en|archive-url=https://web.archive.org/web/20120822132632/http://www.theatlantic.com/magazine/archive/1945/07/as-we-may-think/303881/4/|archive-date=2012-08-22}}</ref> He described this system in an article titled "[[As We May Think]]" in [[The Atlantic|''The Atlantic Monthly'']].<ref>{{Cite web|title=Search Engine History.com|url=http://www.searchenginehistory.com/|access-date=2020-07-02|website=www.searchenginehistory.com}}</ref> The [[memex]] was intended to give a user the capability to overcome the ever-increasing difficulty of locating information in ever-growing centralized indices of scientific work. Vannevar Bush envisioned libraries of research with connected annotations, which are similar to modern [[hyperlink]]s.<ref>{{Cite web|title=Penn State WebAccess Secure Login|url=https://webaccess.psu.edu/?cosign-scripts.libraries.psu.edu&https%3A%2F%2Fscripts.libraries.psu.edu%2Fscripts%2Fezproxyauth.php%3Furl=ezp.2aHR0cHM6Ly9pZWVleHBsb3JlLmllZWUub3JnL3N0YW1wL3N0YW1wLmpzcD90cD0mYXJudW1iZXI9ODUwOTU1MA--|access-date=2020-07-02|website=webaccess.psu.edu|archive-date=2022-01-22|archive-url=https://web.archive.org/web/20220122194212/https://webaccess.psu.edu/?cosign-scripts.libraries.psu.edu&https%3A%2F%2Fscripts.libraries.psu.edu%2Fscripts%2Fezproxyauth.php%3Furl=ezp.2aHR0cHM6Ly9pZWVleHBsb3JlLmllZWUub3JnL3N0YW1wL3N0YW1wLmpzcD90cD0mYXJudW1iZXI9ODUwOTU1MA--|url-status=dead}}</ref>

[[Link analysis]] eventually became a crucial component of search engines through algorithms such as [[Hyper Search]] and [[PageRank]].<ref>{{Cite web|title=The Quest for Correct Information on the Web: Hyper Search Engines|first1=Massimo|last1=Marchiori|work=Proceedings of the Sixth International World Wide Web Conference (WWW6)|date=1997|url=http://www.w3.org/People/Massimo/papers/WWW6/Overview.html|access-date=2021-01-10}}</ref><ref name="AnatomyOfSearch">{{cite web|title=The Anatomy of a Large-Scale Hypertextual Web Search Engine|last1=Brin|first1=Sergey|last2=Page|first2=Larry|work=Proceedings of the Seventh International World Wide Web Conference (WWW7)|date=1998|url=http://ilpubs.stanford.edu:8090/361/1/1998-8.pdf|access-date=2021-01-10|archive-date=2017-07-13|archive-url=https://web.archive.org/web/20170713070157/http://ilpubs.stanford.edu:8090/361/1/1998-8.pdf|url-status=dead}}</ref>

===1990s: Birth of search engines===
The first internet search engines predate the debut of the Web in December 1990: [[WHOIS]] user search dates back to 1982,{{ref RFC|812}} and the [[Knowbot Information Service]] multi-network user search was first implemented in 1989.<ref>{{cite web|url=http://www.cnri.reston.va.us/home/koe/iwooos-full.html|title=Knowbot programming: System support for mobile agents|work=cnri.reston.va.us}}</ref> The first well documented search engine that searched content files, namely [[FTP]] files, was [[Archie search engine|Archie]], which debuted on 10 September 1990.<ref>{{cite web|url=https://groups.google.com/forum/#!msg/comp.archives/LWVA50W8BKk/wyRbF_lDc6cJ|title=[next] An Internet archive server server (was about Lisp)|last=Deutsch|first=Peter|date=September 11, 1990|website=groups.google.com|access-date=2017-12-29}}</ref>

Prior to September 1993, the [[World Wide Web]] was entirely indexed by hand. There was a list of [[webserver]]s edited by [[Tim Berners-Lee]] and hosted on the [[CERN]] [[Web server|webserver]]. One snapshot of the list in 1992 remains,<ref>{{cite web|url=http://www.w3.org/History/19921103-hypertext/hypertext/DataSources/WWW/Servers.html |title=World-Wide Web Servers |publisher=W3C |access-date=2012-05-14}}</ref> but as more and more web servers went online the central list could no longer keep up. On the [[National Center for Supercomputing Applications|NCSA]] site, new servers were announced under the title "What's New!".<ref>{{cite web|url=http://home.mcom.com/home/whatsnew/whats_new_0294.html |title=What's New! February 1994 |publisher=Mosaic Communications Corporation! |access-date=2012-05-14}}</ref>

The first tool used for searching content (as opposed to users) on the [[Internet]] was [[Archie search engine|Archie]].<ref name=LeidenUnivSE>{{cite web |url-status=dead |work=Internet History |title=Search Engines |author1=Search Engine Watch |author-link1=Search Engine Watch |publisher=Universiteit Leiden |location=Netherlands |date=September 2001 |url=http://www.internethistory.leidenuniv.nl/index.php3?c=7 |archive-url=https://web.archive.org/web/20090413030108/http://www.internethistory.leidenuniv.nl/index.php3?c=7 |archive-date=2009-04-13 }}</ref> The name stands for "archive" without the "v".<ref name="2020/09/21pcmag"/> It was created by [[Alan Emtage]],<ref name="2020/09/21pcmag">{{cite web | title = Archie | url = https://www.pcmag.com/encyclopedia/term/archie | publisher=[[PCMag]]| access-date = 2020-09-20 }}</ref><ref>{{cite web | author = Alexandra Samuel| title = Meet Alan Emtage, the Black Technologist Who Invented ARCHIE, the First Internet Search Engine| date = 21 February 2017| url = https://daily.jstor.org/alan-emtage-first-internet-search-engine/ |publisher= [[ITHAKA]]| access-date = 2020-09-20 }}</ref><ref>{{cite web | author = loop news barbados | title = Alan Emtage- a Barbadian you should know | url = http://www.loopnewsbarbados.com/content/alan-emtage-barbadian-you-should-know | publisher = loopnewsbarbados.com | access-date = 2020-09-21 | archive-date = 2020-09-23 | archive-url = https://web.archive.org/web/20200923065914/http://www.loopnewsbarbados.com/content/alan-emtage-barbadian-you-should-know | url-status = dead }}</ref><ref>{{cite web | author = Dino Grandoni, Alan Emtage | title = Alan Emtage: The Man Who Invented The World's First Search Engine (But Didn't Patent It)| date = April 2013| url = https://www.huffingtonpost.co.uk/entry/alan-emtage-search-engine_n_2994090?ri18n=true&guccounter=1&guce_referrer=aHR0cHM6Ly9jb25zZW50LnlhaG9vLmNvbS8&guce_referrer_sig=AQAAABveQefuoczW_8_bxwbOgluVTUPvIfv5s_OP1jMgUJd8MCwKc148lvXb7HAHXY48P_Be6wXMW0LKlLRfQzJNalLpuwnp7F6NpbyDC2BG10OveS2qtubkO0PhJ8-juP3M2a9K2ygbWuoUhOCvO-1NA6-YQKA8BtdZEcsfUUI_M-8S | publisher= [[huffingtonpost]].co.uk|access-date = 2020-09-21 }}</ref> [[computer science]] student at [[McGill University]] in [[Montreal, Quebec]], Canada. The program downloaded the directory listings of all the files located on public anonymous FTP ([[File Transfer Protocol]]) sites, creating a searchable [[database]] of file names; however, [[Archie search engine|Archie Search Engine]] did not index the contents of these sites since the amount of data was so limited it could be readily searched manually.

The rise of [[Gopher (protocol)|Gopher]] (created in 1991 by [[Mark McCahill]] at the [[University of Minnesota]]) led to two new search programs, [[Veronica (search engine)|Veronica]] and [[Jughead (search engine)|Jughead]]. Like Archie, they searched the file names and titles stored in Gopher index systems. Veronica (Very Easy Rodent-Oriented Net-wide Index to Computerized Archives) provided a keyword search of most Gopher menu titles in the entire Gopher listings. Jughead (Jonzy's Universal Gopher Hierarchy Excavation And Display) was a tool for obtaining menu information from specific Gopher servers. While the name of the search engine "[[Archie search engine|Archie Search Engine]]" was not a reference to the [[Archie Comics|Archie comic book]] series, "[[Veronica Lodge|Veronica]]" and "[[Jughead Jones|Jughead]]" are characters in the series, thus referencing their predecessor.

In the summer of 1993, no search engine existed for the web, though numerous specialized catalogs were maintained by hand. [[Oscar Nierstrasz]] at the [[University of Geneva]] wrote a series of [[Perl]] scripts that periodically mirrored these pages and rewrote them into a standard format. This formed the basis for [[W3Catalog]], the web's first primitive search engine, released on September 2, 1993.<ref name="Announcement html">{{cite web |url= http://groups.google.com/group/comp.infosystems.www/browse_thread/thread/2176526a36dc8bd3/2718fd17812937ac?hl=en&lnk=gst&q=Oscar+Nierstrasz#2718fd17812937ac|title=Searchable Catalog of WWW Resources (experimental)|author=Oscar Nierstrasz|date=2 September 1993|author-link=Oscar Nierstrasz}}</ref>

In June 1993, Matthew Gray, then at [[Massachusetts Institute of Technology|MIT]], produced what was probably the first [[web robot]], the [[Perl]]-based [[World Wide Web Wanderer]], and used it to generate an index called "Wandex". The purpose of the Wanderer was to measure the size of the World Wide Web, which it did until late 1995. The web's second search engine [[Aliweb]] appeared in November 1993. Aliweb did not use a [[web robot]], but instead depended on being notified by [[Webmaster|website administrators]] of the existence at each site of an index file in a particular format.

[[JumpStation]] (created in December 1993<ref>{{cite web |url=http://archive.ncsa.uiuc.edu/SDG/Software/Mosaic/Docs/old-whats-new/whats-new-1293.html |archive-url=https://web.archive.org/web/20010620073530/http://archive.ncsa.uiuc.edu/SDG/Software/Mosaic/Docs/old-whats-new/whats-new-1293.html |archive-date=2001-06-20 |title=Archive of NCSA what's new in December 1993 page |date=2001-06-20 |access-date=2012-05-14 |url-status=dead }}</ref> by [[Jonathon Fletcher]]) used a [[web crawler|web robot]] to find web pages and to build its index, and used a [[web form]] as the interface to its query program. It was thus the first [[World Wide Web|WWW]] resource-discovery tool to combine the three essential features of a web search engine (crawling, indexing, and searching) as described below. Because of the limited resources available on the platform it ran on, its indexing and hence searching were limited to the titles and headings found in the [[web page]]s the crawler encountered.

One of the first "all text" crawler-based search engines was [[WebCrawler]], which came out in 1994. Unlike its predecessors, it allowed users to search for any word in any [[web page]], which has become the standard for all major search engines since. It was also the search engine that was widely known by the public. Also, in 1994, [[Lycos]] (which started at [[Carnegie Mellon University]]) was launched and became a major commercial endeavor.

The first popular search engine on the Web was [[Yahoo! Search]].<ref>{{cite web |title=What is first mover? |url=https://searchcio.techtarget.com/definition/first-mover |website=SearchCIO |publisher=[[TechTarget]] |access-date=5 September 2019 |date=September 2005}}</ref> The first product from [[Yahoo!]], founded by [[Jerry Yang]] and [[David Filo]] in January 1994, was a [[Web directory]] called [[Yahoo! Directory]]. In 1995, a search function was added, allowing users to search Yahoo! Directory.<ref>{{cite book |last1=Oppitz |first1=Marcus |last2=Tomsu |first2=Peter |title=Inventing the Cloud Century: How Cloudiness Keeps Changing Our Life, Economy and Technology |date=2017 |publisher=Springer |isbn=9783319611617 |page=238 |url=https://books.google.com/books?id=vrEvDwAAQBAJ&pg=PA238}}</ref><ref>{{cite web |title=Yahoo! Search |url=https://www.yahoo.com/search.html |archive-url=https://web.archive.org/web/19961128070718/http://www.yahoo.com/search.html |url-status=dead |archive-date=28 November 1996 |website=Yahoo! |access-date=5 September 2019 |date=28 November 1996}}</ref> It became one of the most popular ways for people to find web pages of interest, but its search function operated on its web directory, rather than its full-text copies of web pages.

Soon after, a number of search engines appeared and vied for popularity. These included [[Magellan (search engine)|Magellan]], [[Excite (web portal)|Excite]], [[Infoseek]], [[Inktomi (company)|Inktomi]], [[Northern Light Group|Northern Light]], and [[AltaVista]]. Information seekers could also browse the directory instead of doing a keyword-based search.

In 1996, [[Robin Li]] developed the [[RankDex]] site-scoring [[algorithm]] for search engines results page ranking<ref>Greenberg, Andy, [https://www.forbes.com/forbes/2009/1005/technology-baidu-robin-li-man-whos-beating-google.html "The Man Who's Beating Google"], ''Forbes'' magazine, October 5, 2009</ref><ref>Yanhong Li, "Toward a Qualitative Search Engine", ''IEEE Internet Computing'', vol. 2, no. 4, pp. 24–29, July/Aug. 1998, {{doi|10.1109/4236.707687}}</ref><ref name="rankdex">[http://www.rankdex.com/about.html "About: RankDex"], ''rankdex.com''</ref> and received a US patent for the technology.<ref>USPTO, [https://patents.google.com/patent/US5920859 "Hypertext Document Retrieval System and Method"], US Patent number: 5920859, Inventor: Yanhong Li, Filing date: Feb 5, 1997, Issue date: Jul 6, 1999</ref> It was the first search engine that used [[hyperlink]]s to measure the quality of websites it was indexing,<ref>{{cite web |title=Baidu Vs Google: The Twins Of Search Compared |url=https://fourweekmba.com/baidu-vs-google/ |website=FourWeekMBA |access-date=16 June 2019 |date=18 September 2018}}</ref> predating the very similar algorithm patent filed by [[Google]] two years later in 1998.<ref>{{cite web |last1=Altucher |first1=James |title=10 Unusual Things About Google |url=https://www.forbes.com/sites/jamesaltucher/2011/03/18/10-unusual-things-about-google-also-the-worst-vc-decision-i-ever-made/ |date=March 18, 2011 |website=[[Forbes]] |access-date=16 June 2019}}</ref> [[Larry Page]] referenced Li's work in some of his U.S. patents for PageRank.<ref name="patent">{{cite web |title = Method for node ranking in a linked database |url = https://patents.google.com/patent/US6285999 |publisher = Google Patents |access-date = 19 October 2015 |url-status = live |archive-url = https://web.archive.org/web/20151015185034/http://www.google.com/patents/US6285999 |archive-date = 15 October 2015 }}</ref> Li later used his RankDex technology for the [[Baidu]] search engine, which was founded by him in China and launched in 2000.

In 1996, [[Netscape]] was looking to give a single search engine an exclusive deal as the featured search engine on Netscape's web browser. There was so much interest that instead, Netscape struck deals with five of the major search engines: for $5 million a year, each search engine would be in rotation on the Netscape search engine page. The five engines were Yahoo!, Magellan, Lycos, Infoseek, and Excite.<ref>{{Cite web|url=http://files.shareholder.com/downloads/YHOO/701084386x0x27155/9a3b5ed8-9e84-4cba-a1e5-77a3dc606566/YHOO_News_1997_7_8_General.pdf|title=Yahoo! And Netscape Ink International Distribution Deal|access-date=2009-08-12|archive-url=https://web.archive.org/web/20131116112021/http://files.shareholder.com/downloads/YHOO/701084386x0x27155/9a3b5ed8-9e84-4cba-a1e5-77a3dc606566/YHOO_News_1997_7_8_General.pdf|archive-date=2013-11-16|url-status=dead}}</ref><ref>{{cite news |date=1 April 1996|title=Browser Deals Push Netscape Stock Up 7.8% |newspaper=Los Angeles Times |url=https://www.latimes.com/archives/la-xpm-1996-04-01-fi-53780-story.html }}</ref>

[[Google]] adopted the idea of selling search terms in 1998 from a small search engine company named [[Yahoo! Search Marketing|goto.com]]. This move had a significant effect on the search engine business, which went from struggling to one of the most profitable businesses in the Internet.<ref>{{Cite news |last=Oremus |first=Will |date=2013-10-14 |title=Google's Big Break |url=https://slate.com/business/2013/10/googles-big-break-how-bill-gross-goto-com-inspired-the-adwords-business-model.html?utm_source=askpandi&utm_medium=answer_engine |access-date=2025-03-12 |work=Slate |language=en-US |issn=1091-2339}}</ref><ref>{{Cite web |last=Jay |date=1998-02-19 |title=GoTo: The Forgotten Search Engine |url=https://thehistoryoftheweb.com/goto-forgotten-search-engine/?utm_source=askpandi&utm_medium=answer_engine |access-date=2025-03-12 |website=The History of the Web}}</ref>

Search engines were also known as some of the brightest stars in the Internet investing frenzy that occurred in the late 1990s.<ref>{{cite journal |last=Gandal |first=Neil |year=2001 |title=The dynamics of competition in the internet search engine market |journal=International Journal of Industrial Organization |volume=19 |issue=7 |pages=1103–1117 |doi=10.1016/S0167-7187(01)00065-0 |url= http://www.escholarship.org/uc/item/0h17g08v |issn=0167-7187}}</ref> Several companies entered the market spectacularly, receiving record gains during their [[initial public offering]]s. Some have taken down their public search engine and are marketing enterprise-only editions, such as Northern Light. Many search engine companies were caught up in the [[dot-com bubble]], a speculation-driven market boom that peaked in March 2000.

===2000s–present: Post dot-com bubble===
Around 2000, [[Google Search|Google's search engine]] rose to prominence.<ref>{{cite web|url=https://www.google.com/about/company/history/ |title=Our history in depth |access-date=2012-10-31 |url-status=deviated |archive-url= https://web.archive.org/web/20121101210037/https://www.google.com/about/company/history/ |archive-date= November 1, 2012 }}</ref> The company achieved better results for many searches with an algorithm called [[PageRank]], as was explained in the paper ''Anatomy of a Search Engine'' written by [[Sergey Brin]] and [[Larry Page]], the later founders of Google.<ref name="AnatomyOfSearch" /> This [[iterative algorithm]] ranks web pages based on the number and PageRank of other web sites and pages that link there, on the premise that good or desirable pages are linked to more than others. Larry Page's patent for PageRank cites [[Robin Li]]'s earlier [[RankDex]] patent as an influence.<ref name="patent"/><ref name="rankdex"/> Google also maintained a minimalist interface to its search engine. In contrast, many of its competitors embedded a search engine in a [[web portal]]. In fact, the Google search engine became so popular that spoof engines emerged such as [[Mystery Seeker]].

By 2000, [[Yahoo!]] was providing search services based on Inktomi's search engine. Yahoo! acquired Inktomi in 2002, and [[Yahoo! Native|Overture]] (which owned [[AlltheWeb]] and AltaVista) in 2003. Yahoo! switched to Google's search engine until 2004, when it launched its own search engine based on the combined technologies of its acquisitions.

[[Microsoft]] first launched MSN Search in the fall of 1998 using search results from Inktomi. In early 1999, the site began to display listings from [[Looksmart]], blended with results from Inktomi. For a short time in 1999, MSN Search used results from AltaVista instead. In 2004, [[Microsoft]] began a transition to its own search technology, powered by its own [[web crawler]] (called [[msnbot]]).

Microsoft's rebranded search engine, [[Bing (search engine)|Bing]], was launched on June 1, 2009. On July 29, 2009, Yahoo! and Microsoft finalized a deal in which [[Yahoo! Search]] would be powered by Microsoft Bing technology.

{{As of|2019|post=,}} active search engine crawlers include those of Google, [[Sogou]], Baidu, Bing, [[Gigablast]], [[Mojeek]], [[DuckDuckGo]] and [[Yandex]].

== Approach ==
{{anchor|Workings}}
{{main|Search engine technology}}
A search engine maintains the following processes in near real time:<ref>{{cite web |url=https://www.techtarget.com/whatis/definition/search-engine |title=Definition – search engine |website=Techtarget |access-date=1 June 2023}}</ref>
# [[Web crawling]]
# [[Index (search engine)|Indexing]]
# [[Web search query|Searching]]<ref name=Jawadekar2011>{{citation |year=2011 |author=Jawadekar, Waman S |title=Knowledge Management: Text & Cases |chapter=8. Knowledge Management: Tools and Technology |chapter-url=https://books.google.com/books?id=XmGx4J9daUMC&pg=PA278 |page=278 |place=New Delhi |publisher=Tata McGraw-Hill Education Private Ltd |isbn=978-0-07-07-0086-4 |access-date=November 23, 2012 }}</ref>

Web search engines get their information by [[Web crawler|web crawling]] from site to site. The "spider" checks for the standard filename ''[[robots.txt]]'', addressed to it. The robots.txt file contains directives for search spiders, telling it which pages to crawl and which pages not to crawl. After checking for robots.txt and either finding it or not, the spider sends certain information back to be [[Search engine indexing|indexed]] depending on many factors, such as the titles, page content, [[JavaScript]], [[Cascading Style Sheets]] (CSS), headings, or its [[metadata]] in HTML [[meta tags]]. After a certain number of pages crawled, amount of data indexed, or time spent on the website, the spider stops crawling and moves on. "[N]o web crawler may actually crawl the entire reachable web. Due to infinite websites, spider traps, spam, and other exigencies of the real web, crawlers instead apply a crawl policy to determine when the crawling of a site should be deemed sufficient. Some websites are crawled exhaustively, while others are crawled only partially".<ref>Dasgupta, Anirban; Ghosh, Arpita; Kumar, Ravi; Olston, Christopher; Pandey, Sandeep; and Tomkins, Andrew. ''The Discoverability of the Web''. http://www.arpitaghosh.com/papers/discoverability.pdf</ref>

Indexing means associating words and other definable tokens found on web pages to their domain names and [[HTML]]-based fields. The associations are stored in a public database and accessible through web search queries. A query from a user can be a single word, multiple words or a sentence. The index helps find information relating to the query as quickly as possible.<ref name=Jawadekar2011/> Some of the techniques for indexing, and [[search engine cache|caching]] are trade secrets, whereas web crawling is a straightforward process of visiting all sites on a systematic basis.

Between visits by the ''spider'', the [[Cache (computing)|cached]] version of the page (some or all the content needed to render it) stored in the search engine working memory is quickly sent to an inquirer. If a visit is overdue, the search engine can just act as a [[web proxy]] instead. In this case, the page may differ from the search terms indexed.<ref name=Jawadekar2011/> The cached page holds the appearance of the version whose words were previously indexed, so a cached version of a page can be useful to the website when the actual page has been lost, but this problem is also considered a mild form of [[linkrot]].

<!-- perhaps at web cache:
, and Google's handling of it increases [[usability]] by satisfying [[user expectations]] that the search terms will be on the returned webpage. This satisfies the [[principle of least astonishment]], since the user normally expects that the search terms will be on the returned pages. Increased search relevance makes these cached pages very useful as they may contain data that may no longer be available elsewhere.{{Citation needed|date=November 2012}}
-->
[[File:WebCrawlerArchitecture.svg|thumb|High-level architecture of a standard Web crawler]]
Typically, when a user enters a [[web search query|query]] into a search engine it is a few [[Keyword (Internet search)|keywords]].<ref name="Jansen2000">Jansen, B. J., Spink, A., and Saracevic, T. 2000. [https://faculty.ist.psu.edu/jjansen/academic/pubs/jansen_real_life_real_users_and_real_needs.pdf Real life, real users, and real needs: A study and analysis of user queries on the web]. Information Processing & Management. 36(2), 207–227.</ref> The [[inverted index|index]] already has the names of the sites containing the keywords, and these are instantly obtained from the index. The real processing load is in generating the web pages that are the search results list: Every page in the entire list must be [[weighting|weighted]] according to information in the indexes.<ref name=Jawadekar2011/> Then the top search result item requires the lookup, reconstruction, and markup of the ''[[Snippet (programming)|snippets]]'' showing the context of the keywords matched. These are only part of the processing each search results web page requires, and further pages (next to the top) require more of this post-processing.

Beyond simple keyword lookups, search engines offer their own [[Graphical user interface|GUI]]- or command-driven operators and search parameters to refine the search results. These provide the necessary controls for the user engaged in the feedback loop users create by ''filtering'' and ''weighting'' while refining the search results, given the initial pages of the first search results. For example, from 2007 the Google.com search engine has allowed one to ''filter'' by date by clicking "Show search tools" in the leftmost column of the initial search results page, and then selecting the desired date range.<ref>{{cite web|last1=Chitu|first1=Alex|title=Easy Way to Find Recent Web Pages|url=http://googlesystem.blogspot.com/2007/08/easy-way-to-find-recent-web-pages.html|website=Google Operating System|access-date=22 February 2015|date=August 30, 2007}}</ref> It is also possible to ''weight'' by date because each page has a modification time. Most search engines support the use of the [[Boolean operator (computer programming)|Boolean operator]]s AND, OR and NOT to help end users refine the [[web search query|search query]]. Boolean operators are for literal searches that allow the user to refine and extend the terms of the search. The engine looks for the words or phrases exactly as entered. Some search engines provide an advanced feature called [[Proximity search (text)|proximity search]], which allows users to define the distance between keywords.<ref name=Jawadekar2011/> There is also [[Concept search|concept-based searching]] where the research involves using statistical analysis on pages containing the words or phrases the user searches for.

The usefulness of a search engine depends on the [[relevance (information retrieval)|relevance]] of the ''result set'' it gives back. While there may be millions of web pages that include a particular word or phrase, some pages may be more relevant, popular, or authoritative than others. Most search engines employ methods to [[rank order|rank]] the results to provide the "best" results first. How a search engine decides which pages are the best matches, and what order the results should be shown in, varies widely from one engine to another.<ref name=Jawadekar2011/> The methods also change over time as Internet usage changes and new techniques evolve. There are two main types of search engine that have evolved: one is a system of predefined and hierarchically ordered keywords that humans have programmed extensively. The other is a system that generates an "[[inverted index]]" by analyzing texts it locates. This first form relies much more heavily on the computer itself to do the bulk of the work.

Most Web search engines are commercial ventures supported by [[advertising]] revenue and thus some of them allow advertisers to [[paid inclusion|have their listings ranked higher]] in search results for a fee. Search engines that do not accept money for their search results make money by running [[contextual advertising|search related ads]] alongside the regular search engine results. The search engines make money every time someone clicks on one of these ads.<ref>{{cite web|title=how search engine works?|url=http://globalforumonline.com/detail/how-does-search-engine-works/|publisher= GFO | access-date = 26 June 2018}}</ref>

=== Local search ===
[[Local search (Internet)|Local search]] is the process that optimizes the efforts of local businesses. They focus on ensuring consistent search results. It is important because many people determine where they plan to go and what to buy based on their searches.<ref>{{Cite web|url=https://www.searchenginejournal.com/local-seo/what-is-local-seo-why-local-search-is-important/|title=What Is Local SEO & Why Local Search Is Important|website=Search Engine Journal|language=en|access-date=2020-04-26}}</ref>

==Market share==
{{As of|2022|01|post=,}} [[Google Search|Google]] is by far the world's most used search engine, with a market share of 90%, and the world's other most used search engines were [[Microsoft Bing|Bing]] at 4%, [[Yandex Search|Yandex]] at 2%, [[Yahoo! Search|Yahoo!]] at 1%. Other search engines not listed have less than a 3% market share.<ref name="NMS">{{cite web | url=https://www.similarweb.com/engines/ | title=Search Engine Market Share Worldwide | access-date=19 February 2024 | website=Similarweb Top search engines}}</ref> In 2024, Google's dominance was ruled an illegal monopoly in a case brought by the US Department of Justice.<ref>{{cite web | last=Kerr | first=Dara | title=U.S. v. Google: As landmark 'monopoly power' trial closes, here's what to look for | website=[[NPR]] | date=2024-05-02 | url=https://www.npr.org/2024/05/02/1248152695/google-doj-monopoly-trial-antitrust-closing-arguments}}</ref>

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=== Russia and East Asia ===
{{update section|date=December 2023}}
In Russia, [[Yandex]] has a market share of 62.6%, compared to Google's 28.3%. Yandex is the second most used search engine on smartphones in Asia and Europe.<ref>{{cite web|url=http://www.liveinternet.ru/stat/ru/searches.html?slice=ru;period=week|title=Live Internet - Site Statistics|publisher=Live Internet|access-date=2014-06-04}}</ref> In China, Baidu is the most popular search engine.<ref>{{cite news |url=https://www.theguardian.com/world/2014/jun/03/chinese-technology-companies-huawei-dominate-world|title=The Chinese technology companies poised to dominate the world |newspaper=The Guardian |author=Arthur, Charles |date=2014-06-03 |access-date=2014-06-04}}</ref> South Korea-based search portal [[Naver]] is used for 62.8% of online searches in the country.<ref>{{cite news|url=https://blogs.wsj.com/korearealtime/2014/05/21/how-naver-hurts-companies-productivity/|title=How Naver Hurts Companies' Productivity |newspaper=The Wall Street Journal |date=2014-05-21|access-date=2014-06-04}}</ref> [[Yahoo! Japan]] and [[Yahoo! Search|Yahoo! Taiwan]] are the most popular choices for Internet searches in Japan and Taiwan, respectively.<ref>{{cite web |title=Age of Internet Empires |url=https://geography.oii.ox.ac.uk/age-of-internet-empires/ |publisher=Oxford Internet Institute |access-date=15 August 2019}}</ref> China is one of few countries where Google is not in the top three web search engines for market share. Google was previously more popular in China, but withdrew significantly after a disagreement with the government over censorship and a cyberattack. Bing, however, is in the top three web search engines with a market share of 14.95%. Baidu is top with 49.1% of the market share.<ref>{{Cite web |url=https://www.theatlantic.com/technology/archive/2016/01/why-google-quit-china-and-why-its-heading-back/424482/|title=Why Google Quit China—and Why It's Heading Back |last=Waddell|first=Kaveh|date=2016-01-19|website=The Atlantic|language=en-US|access-date=2020-04-26}}</ref>{{Failed verification|date=April 2024|reason=The statement "But Bing is in top three web search engine with a market share of 14.95%. Baidu is on top with 49.1% market share." has nothing to do with any of the linked article's content.}}

===Europe===
Most countries' markets in the European Union are dominated by Google, except for the [[Czech Republic]], where [[Seznam]] is a strong competitor.<ref>{{cite web | last=Kissane | first=Dylan | title=Seznam Takes on Google in the Czech Republic | website=DOZ | date=2015-08-05 | url=https://www.doz.com/search-engine/seznam-search-engine}}</ref>

The search engine [[Qwant]] is based in [[Paris]], [[France]], where it attracts most of its 50 million monthly registered users from.

== Search engine bias ==
{{Further|Algorithmic bias}}
Although search engines are programmed to rank websites based on some combination of their popularity and relevancy, empirical studies indicate various political, economic, and social biases in the information they provide<ref>Segev, El (2010). [https://books.google.com/books?id=_Y9wAgAAQBAJ&q=bias Google and the Digital Divide: The Biases of Online Knowledge], Oxford: Chandos Publishing.</ref><ref name=vaughan-thelwall>{{cite journal|last=Vaughan|first=Liwen|author2=Mike Thelwall |title=Search engine coverage bias: evidence and possible causes|journal=Information Processing & Management|year=2004|volume=40|issue=4|pages=693–707|doi=10.1016/S0306-4573(03)00063-3|citeseerx=10.1.1.65.5130|s2cid=18977861 }}</ref> and the underlying assumptions about the technology.<ref>Jansen, B. J. and Rieh, S. (2010) [https://faculty.ist.psu.edu/jjansen/academic/jansen_theoretical_constructs.pdf The Seventeen Theoretical Constructs of Information Searching and Information Retrieval]. Journal of the American Society for Information Sciences and Technology. 61(8), 1517–1534.</ref> These biases can be a direct result of economic and commercial processes (e.g., companies that advertise with a search engine can become also more popular in its [[organic search]] results), and political processes (e.g., the removal of search results to comply with local laws).<ref>Berkman Center for Internet & Society (2002), [http://cyber.law.harvard.edu/filtering/china/google-replacements/ "Replacement of Google with Alternative Search Systems in China: Documentation and Screen Shots"], Harvard Law School.</ref> For example, Google will not surface certain [[neo-Nazism|neo-Nazi]] websites in France and Germany, where [[Holocaust denial]] is illegal.

Biases can also be a result of social processes, as search engine algorithms are frequently designed to exclude non-normative viewpoints in favor of more "popular" results.<ref>{{cite journal|last=Introna|first=Lucas|author2=Helen Nissenbaum |title=Shaping the Web: Why the Politics of Search Engines Matters|journal=The Information Society|year=2000|volume=16|issue=3|pages=169–185|doi=10.1080/01972240050133634|citeseerx=10.1.1.24.8051|s2cid=2111039|author2-link=Helen Nissenbaum}}</ref> Indexing algorithms of major search engines skew towards coverage of U.S.-based sites, rather than websites from non-U.S. countries.<ref name=vaughan-thelwall />

[[Google Bombing]] is one example of an attempt to manipulate search results for political, social or commercial reasons.

Several scholars have studied the cultural changes triggered by search engines,<ref>{{Cite book|title = Google and the Culture of Search|url = https://archive.org/details/googlecultureofs0000hill|url-access = registration|publisher = Routledge|date = 2012-10-12|isbn = 9781136933066|first1 = Ken|last1 = Hillis|first2 = Michael|last2 = Petit|first3 = Kylie|last3 = Jarrett}}</ref> and the representation of certain controversial topics in their results, such as [[terrorism in Ireland]],<ref>{{Cite book|volume = 14|publisher = Springer Berlin Heidelberg|date = 2008-01-01|isbn = 978-3-540-75828-0|pages = 151–175|series = Information Science and Knowledge Management|doi = 10.1007/978-3-540-75829-7_10|first = P.|last = Reilly| title=Web Search | chapter='Googling' Terrorists: Are Northern Irish Terrorists Visible on Internet Search Engines? |s2cid = 84831583|editor-first = Prof Dr Amanda|editor-last = Spink|editor-first2 = Michael|editor-last2 = Zimmer|bibcode = 2008wsis.book..151R}}</ref> [[climate change denial]],<ref>[[Hiroko Tabuchi]], "[https://www.nytimes.com/2017/12/29/climate/google-search-climate-change.html How Climate Change Deniers Rise to the Top in Google Searches]", The New York Times, Dec. 29, 2017. Retrieved November 14, 2018.</ref> and [[Conspiracy theory|conspiracy theories]].<ref>{{cite journal|title = Google chemtrails: A methodology to analyze topic representation in search engines|journal = First Monday|volume = 20|issue = 7|last = Ballatore|first = A|doi = 10.5210/fm.v20i7.5597|year = 2015 | doi-access=free }}</ref>

== Customized results and filter bubbles ==

There has been concern raised that search engines such as Google and Bing provide customized results based on the user's activity history, leading to what has been termed echo chambers or [[filter bubble]]s by [[Eli Pariser]] in 2011.<ref>{{Cite book |last=Pariser |first=Eli |url=https://www.worldcat.org/oclc/682892628 |title=The filter bubble : what the Internet is hiding from you |date=2011 |publisher=Penguin Press |isbn=978-1-59420-300-8 |location=New York |oclc=682892628}}</ref> The argument is that search engines and social media platforms use [[algorithm]]s to selectively guess what information a user would like to see, based on information about the user (such as location, past click behavior and search history). As a result, websites tend to show only information that agrees with the user's past viewpoint. According to [[Eli Pariser]] users get less exposure to conflicting viewpoints and are isolated intellectually in their own informational bubble. Since this problem has been identified, competing search engines have emerged that seek to avoid this problem by not tracking or "bubbling" users, such as [[DuckDuckGo]]. However many scholars have questioned Pariser's view, finding that there is little evidence for the filter bubble.<ref>{{Cite journal|title = In Worship of an Echo|journal = IEEE Internet Computing|date = 2014-07-01|issn = 1089-7801|pages = 79–83|volume = 18|issue = 4|doi = 10.1109/MIC.2014.71|first = K.|last = O'Hara|s2cid = 37860225|doi-access = free}}</ref><ref name=":0">{{Cite journal |last=Bruns |first=Axel |date=2019-11-29 |title=Filter bubble |url=https://policyreview.info/node/1426 |journal=Internet Policy Review |language=en |volume=8 |issue=4 |doi=10.14763/2019.4.1426 |s2cid=211483210 |issn=2197-6775|doi-access=free |hdl=10419/214088 |hdl-access=free }}</ref><ref name=":1">{{Cite journal |last1=Haim |first1=Mario |last2=Graefe |first2=Andreas |last3=Brosius |first3=Hans-Bernd |date=2018 |title=Burst of the Filter Bubble? |journal=Digital Journalism |volume=6 |issue=3 |pages=330–343 |doi=10.1080/21670811.2017.1338145 |s2cid=168906316 |issn=2167-0811|doi-access=free }}</ref> On the contrary, a number of studies trying to verify the existence of filter bubbles have found only minor levels of personalization in search,<ref name=":1" /> that most people encounter a range of views when browsing online, and that Google news tends to promote mainstream established news outlets.<ref>{{Cite journal |last1=Nechushtai |first1=Efrat |last2=Lewis |first2=Seth C. |date=2019 |title=What kind of news gatekeepers do we want machines to be? Filter bubbles, fragmentation, and the normative dimensions of algorithmic recommendations |url=https://linkinghub.elsevier.com/retrieve/pii/S0747563218303650 |journal=Computers in Human Behavior |language=en |volume=90 |pages=298–307 |doi=10.1016/j.chb.2018.07.043|s2cid=53774351 }}</ref><ref name=":0" />

== Religious search engines ==
The global growth of the Internet and electronic media in the [[Arab]] and [[Muslim]] world during the last decade has encouraged Islamic adherents in [[Middle East|the Middle East]] and [[Indian subcontinent|Asian sub-continent]], to attempt their own search engines, their own filtered search portals that would enable users to perform [[Content-control software|safe searches]]. More than usual ''safe search'' filters, these Islamic web portals categorizing websites into being either "[[halal]]" or "[[haram]]", based on interpretation of [[Sharia|Sharia law]]. [[ImHalal]] came online in September 2011. [[Halalgoogling]] came online in July 2013. These use [[haram]] filters on the collections from [[Google]] and [[Bing (search engine)|Bing]] (and others).<ref>{{cite web |url=http://news.msn.com/science-technology/new-islam-approved-search-engine-for-muslims |title=New Islam-approved search engine for Muslims |publisher=News.msn.com |access-date=2013-07-11 |archive-url=https://web.archive.org/web/20130712023215/http://news.msn.com/science-technology/new-islam-approved-search-engine-for-muslims |archive-date=2013-07-12 |url-status=dead }}</ref>

While lack of investment and slow pace in technologies in the Muslim world has hindered progress and thwarted success of an Islamic search engine, targeting as the main consumers Islamic adherents, projects like [[Muxlim]] (a Muslim lifestyle site) received millions of dollars from investors like Rite Internet Ventures, and it also faltered. Other religion-oriented search engines are Jewogle, the Jewish version of Google,<ref>{{Cite web | url=http://www.jewogle.com/faq/ | title=Jewogle - FAQ | access-date=2019-02-06 | archive-date=2019-02-07 | archive-url=https://web.archive.org/web/20190207015631/http://www.jewogle.com/faq/ | url-status=dead }}</ref> and Christian search engine SeekFind.org. SeekFind filters sites that attack or degrade their faith.<ref>{{cite web|url=http://allchristiannews.com/halalgoogling-muslims-get-their-own-sin-free-google-should-christians-have-christian-google/|title=Halalgoogling: Muslims Get Their Own "sin free" Google; Should Christians Have Christian Google? - Christian Blog|work=Christian Blog|date=2013-07-25|access-date=2014-09-13|archive-date=2014-09-13|archive-url=https://web.archive.org/web/20140913102516/http://allchristiannews.com/halalgoogling-muslims-get-their-own-sin-free-google-should-christians-have-christian-google/|url-status=dead}}</ref>

== Search engine submission ==
Web search engine submission is a process in which a webmaster submits a website directly to a search engine. While search engine submission is sometimes presented as a way to promote a website, it generally is not necessary because the major search engines use web crawlers that will eventually find most web sites on the Internet without assistance. They can either submit one web page at a time, or they can submit the entire site using a [[sitemap]], but it is normally only necessary to submit the [[home page]] of a web site as search engines are able to crawl a well designed website. There are two remaining reasons to submit a web site or web page to a search engine: to add an entirely new web site without waiting for a search engine to discover it, and to have a web site's record updated after a substantial redesign.

Some search engine submission software not only submits websites to multiple search engines, but also adds links to websites from their own pages. This could appear helpful in increasing a website's [[ranking (information retrieval)|ranking]], because external links are one of the most important factors determining a website's ranking. However, John Mueller of [[Google]] has stated that this "can lead to a tremendous number of unnatural links for your site" with a negative impact on site ranking.<ref name="CanBeHarmful">{{cite news |last=Schwartz |first=Barry |author-link=Barry Schwartz (technologist) |url=https://www.seroundtable.com/search-engine-submission-google-15906.html |title=Google: Search Engine Submission Services Can Be Harmful |work=[[Search Engine Roundtable]] |date=2012-10-29 |access-date=2016-04-04 }}</ref>

== Comparison to social bookmarking ==
{{trim|{{#section-h:Social bookmarking|Comparison with search engines}}}}

== Technology ==
{{cleanup split|Search engine technology#Web search engines|21=section|date=November 2022}}

===Archie===
The first web search engine was [[Archie (search engine)|Archie]], created in 1990<ref name="intelligent-technologies">{{cite book|author1=Priti Srinivas Sajja|author2=Rajendra Akerkar|title=Intelligent technologies for web applications|date=2012|publisher=CRC Press|location=Boca Raton|isbn=978-1-4398-7162-1|page=87|url=https://books.google.com/books?id=HqXxoWK7tucC&q=the+University+of+Nevada+System+Computing+Services+group+developed+Veronica.&pg=PA87|accessdate=3 June 2014}}</ref> by [[Alan Emtage]], a student at [[McGill University]] in Montreal. The author originally wanted to call the program "archives", but had to shorten it to comply with the Unix world standard of assigning programs and files short, cryptic names such as grep, cat, troff, sed, awk, perl, and so on.{{cn|date=June 2025}}

The primary method of storing and retrieving files was via the [[File Transfer Protocol]] (FTP). This was (and still is) a system that specified a common way for computers to exchange files over the Internet. It works like this: Some administrator decides that he wants to make files available from his computer. He sets up a program on his computer, called an FTP server. When someone on the Internet wants to retrieve a file from this computer, he or she connects to it via another program called an FTP client. Any FTP client program can connect with any FTP server program as long as the client and server programs both fully follow the specifications set forth in the FTP protocol.

Initially, anyone who wanted to share a file had to set up an FTP server in order to make the file available to others. Later, "anonymous" FTP sites became repositories for files, allowing all users to post and retrieve them.

Even with archive sites, many important files were still scattered on small FTP servers. These files could be located only by the Internet equivalent of word of mouth: Somebody would post an e-mail to a message list or a discussion forum announcing the availability of a file.

Archie changed all that. It combined a script-based data gatherer, which fetched site listings of anonymous FTP files, with a regular expression matcher for retrieving file names matching a user query. (4) In other words, Archie's gatherer scoured FTP sites across the Internet and indexed all of the files it found. Its regular expression matcher provided users with access to its database.<ref name="wileyhistory">{{cite web|title=A History of Search Engines|url=http://www.wiley.com/legacy/compbooks/sonnenreich/history.html|publisher=Wiley|accessdate=1 June 2014}}</ref>

===Veronica===
In 1993, the University of Nevada System Computing Services group developed [[Veronica (search engine)|Veronica]].<ref name="intelligent-technologies"/> It was created as a type of searching device similar to Archie but for Gopher files. Another Gopher search service, called Jughead, appeared a little later, probably for the sole purpose of rounding out the comic-strip triumvirate. Jughead is an acronym for Jonzy's Universal Gopher Hierarchy Excavation and Display, although, like Veronica, it is probably safe to assume that the creator backed into the acronym. Jughead's functionality was pretty much identical to Veronica's, although it appears to be a little rougher around the edges.<ref name="wileyhistory"/>

===The Lone Wanderer===
The [[World Wide Web Wanderer]], developed by Matthew Gray in 1993<ref>{{cite book|author1=Priti Srinivas Sajja|author2=Rajendra Akerkar|title=Intelligent technologies for web applications|date=2012|publisher=CRC Press|location=Boca Raton|isbn=978-1-4398-7162-1|page=86|url=https://books.google.com/books?id=HqXxoWK7tucC&q=the+University+of+Nevada+System+Computing+Services+group+developed+Veronica.&pg=PA87|accessdate=3 June 2014}}</ref> was the first robot on the Web and was designed to track the Web's growth. Initially, the Wanderer counted only Web servers, but shortly after its introduction, it started to capture URLs as it went along. The database of captured URLs became the Wandex, the first web database.

Matthew Gray's Wanderer created quite a controversy at the time, partially because early versions of the software ran rampant through the Net and caused a noticeable netwide performance degradation. This degradation occurred because the Wanderer would access the same page hundreds of times a day. The Wanderer soon amended its ways, but the controversy over whether robots were good or bad for the Internet remained.

In response to the Wanderer, Martijn Koster created Archie-Like Indexing of the Web, or ALIWEB, in October 1993. As the name implies, ALIWEB was the HTTP equivalent of Archie, and because of this, it is still unique in many ways.

ALIWEB does not have a web-searching robot. Instead, webmasters of participating sites post their own index information for each page they want listed. The advantage to this method is that users get to describe their own site, and a robot does not run about eating up Net bandwidth. The disadvantages of ALIWEB are more of a problem today. The primary disadvantage is that a special indexing file must be submitted. Most users do not understand how to create such a file, and therefore they do not submit their pages. This leads to a relatively small database, which meant that users are less likely to search ALIWEB than one of the large bot-based sites. This Catch-22 has been somewhat offset by incorporating other databases into the ALIWEB search, but it still does not have the mass appeal of search engines such as Yahoo! or Lycos.<ref name="wileyhistory"/>

===Excite===
[[Excite (web portal)|Excite]], initially called Architext, was started by six Stanford undergraduates in February 1993. Their idea was to use statistical analysis of word relationships in order to provide more efficient searches through the large amount of information on the Internet.
Their project was fully funded by mid-1993. Once funding was secured. they released a version of their search software for webmasters to use on their own web sites. At the time, the software was called Architext, but it now goes by the name of Excite for Web Servers.<ref name="wileyhistory"/>

Excite was the first serious commercial search engine which launched in 1995.<ref>{{cite web|title=The Major Search Engines|url=http://www.pccua.edu/kholland/major_search_engines.htm|accessdate=1 June 2014|date=21 January 2014|archive-date=5 June 2014|archive-url=https://web.archive.org/web/20140605052335/http://www.pccua.edu/kholland/major_search_engines.htm|url-status=dead}}</ref> It was developed in Stanford and was purchased for $6.5 billion by @Home. In 2001 Excite and @Home went bankrupt and [[InfoSpace]] bought Excite for $10 million.

Some of the first analysis of web searching was conducted on search logs from Excite<ref>Jansen, B. J., Spink, A., Bateman, J., and Saracevic, T. 1998. [https://faculty.ist.psu.edu/jjansen/academic/jansen_sigir_forum.pdf Real life information retrieval: A study of user queries on the web]. SIGIR Forum, 32(1), 5 -17.</ref><ref name="Jansen2000" />

===Yahoo!===
In April 1994, two Stanford University Ph.D. candidates, [[David Filo]] and [[Jerry Yang (entrepreneur)|Jerry Yang]], created some pages that became rather popular. They called the collection of pages [[Yahoo!]] Their official explanation for the name choice was that they considered themselves to be a pair of yahoos.

As the number of links grew and their pages began to receive thousands of hits a day, the team created ways to better organize the data. In order to aid in data retrieval, Yahoo! (www.yahoo.com) became a searchable directory. The search feature was a simple database search engine. Because Yahoo! entries were entered and categorized manually, Yahoo! was not really classified as a search engine. Instead, it was generally considered to be a searchable directory. Yahoo! has since automated some aspects of the gathering and classification process, blurring the distinction between engine and directory.

The Wanderer captured only URLs, which made it difficult to find things that were not explicitly described by their URL. Because URLs are rather cryptic to begin with, this did not help the average user. Searching Yahoo! or the Galaxy was much more effective because they contained additional descriptive information about the indexed sites.

===Lycos===
At Carnegie Mellon University during July 1994, Michael Mauldin, on leave from CMU, developed the [[Lycos]] search engine.

===Types of web search engines===
Search engines on the web are sites enriched with facility to search the content stored on other sites. There is difference in the way various search engines work, but they all perform three basic tasks.<ref>{{cite book|author1=Priti Srinivas Sajja|author2=Rajendra Akerkar|title=Intelligent technologies for web applications|date=2012|publisher=CRC Press|location=Boca Raton|isbn=978-1-4398-7162-1|page=85|url=https://books.google.com/books?id=HqXxoWK7tucC&q=the+University+of+Nevada+System+Computing+Services+group+developed+Veronica.&pg=PA87|accessdate=3 June 2014}}</ref>

# Finding and selecting full or partial content based on the keywords provided.
# Maintaining index of the content and referencing to the location they find
# Allowing users to look for words or combinations of words found in that index.

The process begins when a user enters a query statement into the system through the interface provided.

{| class="wikitable"
|-
! Type
! Example
! Description
|-
| Conventional
| librarycatalog
| Search by keyword, title, author, etc.
|-
| Text-based
| Google, Bing, Yahoo!
| Search by keywords. Limited search using queries in natural language.
|-
| [[voice search|Voice-based]]
| Google, Bing, Yahoo!
| Search by keywords. Limited search using queries in natural language.
|-
| [[Multimedia search]]
| QBIC, WebSeek, SaFe
| [[content-based image retrieval|Search by visual appearance]] (shapes, colors,..)
|-
| Q/A
| [[Stack Exchange]], NSIR
| Search in (restricted) natural language
|-
| Clustering Systems
| Vivisimo, Clusty
|
|-
| Research Systems
| Lemur, Nutch
|
|}

There are basically three types of search engines: Those that are powered by robots (called [[web crawler|crawler]]s; ants or spiders) and those that are powered by human submissions; and those that are a hybrid of the two.

Crawler-based search engines are those that use automated software agents (called crawlers) that visit a Web site, read the information on the actual site, read the site's meta tags and also follow the links that the site connects to performing indexing on all linked Web sites as well. The crawler returns all that information back to a central depository, where the data is indexed. The crawler will periodically return to the sites to check for any information that has changed. The frequency with which this happens is determined by the administrators of the search engine.

Human-powered search engines rely on humans to submit information that is subsequently indexed and catalogued. Only information that is submitted is put into the index.

In both cases, when a user queries a search engine to locate information, they're actually searching through the index that the search engine has created —they are not actually searching the Web. These indices are giant databases of information that is collected and stored and subsequently searched. This explains why sometimes a search on a commercial search engine, such as Yahoo! or Google, will return results that are, in fact, dead links. Since the search results are based on the index, if the index has not been updated since a Web page became invalid the search engine treats the page as still an active link even though it no longer is. It will remain that way until the index is updated.

So why will the same search on different search engines produce different results? Part of the answer to that question is because not all indices are going to be exactly the same. It depends on what the spiders find or what the humans submitted. But more important, not every search engine uses the same algorithm to search through the indices. The algorithm is what the search engines use to determine the [[relevance (information retrieval)|relevance]] of the information in the index to what the user is searching for.

One of the elements that a search engine algorithm scans for is the frequency and location of keywords on a Web page. Those with higher frequency are typically considered more relevant. But search engine technology is becoming sophisticated in its attempt to discourage what is known as keyword stuffing, or spamdexing.

Another common element that algorithms analyze is the way that pages link to other pages in the Web. By analyzing how pages link to each other, an engine can both determine what a page is about (if the keywords of the linked pages are similar to the keywords on the original page) and whether that page is considered "important" and deserving of a boost in ranking. Just as the technology is becoming increasingly sophisticated to ignore keyword stuffing, it is also becoming more savvy to Web masters who build artificial links into their sites in order to build an artificial ranking.

Modern web search engines are highly intricate software systems that employ technology that has evolved over the years. There are a number of sub-categories of search engine software that are separately applicable to specific 'browsing' needs. These include web search engines (e.g. [[Google]]), database or structured data search engines (e.g. [[Dieselpoint]]), and mixed search engines or enterprise search. The more prevalent search engines, such as Google and [[Yahoo!]], utilize hundreds of thousands computers to process trillions of web pages in order to return fairly well-aimed results. Due to this high volume of queries and text processing, the software is required to run in a highly dispersed environment with a high degree of superfluity.

Another category of search engines is scientific search engines. These are search engines which search scientific literature. The best known example is Google Scholar. Researchers are working on improving search engine technology by making them understand the content element of the articles, such as extracting theoretical constructs or key research findings.<ref>{{Cite journal|last1=Li|first1=Jingjing|last2=Larsen|first2=Kai|last3=Abbasi|first3=Ahmed|date=2020-12-01|title=TheoryOn: A Design Framework and System for Unlocking Behavioral Knowledge Through Ontology Learning|url=https://misq.org/theoryon-a-design-framework-and-system-for-unlocking-behavioral-knowledge-through-ontology-learning.html|journal=MIS Quarterly|volume=44|issue=4|pages=1733–1772|doi=10.25300/MISQ/2020/15323|s2cid=219401379 }}</ref>

== See also ==

{{columns-list|
* [[Comparison of web search engines]]
* [[Filter bubble]]
* [[Google effect]]
* [[Information retrieval]]
* [[Internet search engines and libraries|Use of web search engines in libraries]]
* [[Itpints]]
* [[List of search engines]]
*[[List of academic databases and search engines]]
* [[Question answering]]
* [[Search engine manipulation effect]]
* [[Search engine privacy]]
* [[Semantic Web]]
* [[Spell checker]]
* [[Timeline of web search engines]]
* [[Web development tools]]
* [[Web query]]
* [[Wikipedia:Search engine test]], for a tutorial on using search engines for researching Wikipedia articles}}

== References ==
{{reflist}}

== Further reading ==
* {{cite journal | author1 =Steve Lawrence |author2=C. Lee Giles | year =1999| title =Accessibility of information on the web | journal =[[Nature (journal)|Nature]] | volume =400 | issue =6740| doi =10.1038/21987 | pmid =10428673 | pages =107–9 | bibcode =1999Natur.400..107L| s2cid =4347646| doi-access =free }}
* Bing Liu (2007), ''[http://www.cs.uic.edu/~liub/WebMiningBook.html Web Data Mining: Exploring Hyperlinks, Contents and Usage Data].'' Springer,{{ISBN|3-540-37881-2}}
* [[Judit Bar-Ilan|Bar-Ilan, J.]] (2004). The use of Web search engines in information science research. ARIST, 38, 231–288.
* {{cite book | first =Mark | last =Levene | year =2005 | title =An Introduction to Search Engines and Web Navigation | publisher =Pearson }}
* {{cite book | first =Randolph | last =Hock | year =2007 | title =The Extreme Searcher's Handbook}}{{ISBN|978-0-910965-76-7}}
* {{cite journal | author =Javed Mostafa |date= February 2005 | title =Seeking Better Web Searches | journal =[[Scientific American]] | volume =292| issue =2| pages =66–73| doi =10.1038/scientificamerican0205-66| bibcode =2005SciAm.292b..66M}}
* {{cite journal |last=Ross |first=Nancy |author2=Wolfram, Dietmar |year=2000 |title=End user searching on the Internet: An analysis of term pair topics submitted to the Excite search engine |journal=Journal of the American Society for Information Science |volume=51 |issue=10 |pages=949–958 |doi=10.1002/1097-4571(2000)51:10<949::AID-ASI70>3.0.CO;2-5}}
* {{cite journal |last1=Xie |first1=M. |year=1998 |title=Quality dimensions of Internet search engines |journal=Journal of Information Science |volume=24 |issue=5 |pages=365–372 |doi=10.1177/016555159802400509 |display-authors=1 |last2=Wang |first2=H. |last3=Goh |first3=T. N. |s2cid=34686531 }}
*{{cite book|title=Information Retrieval: Implementing and Evaluating Search Engines|url=http://www.ir.uwaterloo.ca/book/|year=2010|publisher=MIT Press|author8=Stefan Büttcher, Charles L. A. Clarke, and Gordon V. Cormack|access-date=2010-08-07|archive-date=2020-10-05|archive-url=https://web.archive.org/web/20201005195805/http://www.ir.uwaterloo.ca/book/|url-status=dead}}
* Yeo, ShinJoung. (2023) ''Behind the Search Box: Google and the Global Internet Industry'' (U of Illinois Press, 2023) {{ISBN|0-252-08712-7}} {{jstor|4116455}}

== External links ==
{{commons category|Internet search engines}}
{{wikiversity|Search Engines}}

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