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			<h1 id="firstHeading" class="firstHeading" lang="en"><span dir="auto">Web search engine</span></h1>
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				<div id="siteSub">From Wikipedia, the free encyclopedia</div>
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				<div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"><div class="dablink">"Search engine" redirects here. For other uses, see <a href="/wiki/Search_engine_(disambiguation)" title="Search engine (disambiguation)">Search engine (disambiguation)</a>.</div>
<p>A <b>web search engine</b> is software code that is designed to search for information on the <a href="/wiki/World_Wide_Web" title="World Wide Web">World Wide Web</a>. The search results are generally presented in a line of results often referred to as <a href="/wiki/Search_engine_results_pages" title="Search engine results pages" class="mw-redirect">search engine results pages</a> (SERP's). The information may be a specialist in <a href="/wiki/Web_page" title="Web page">web pages</a>, images, information and other types of files. Some search engines also <a href="/wiki/Data_mining" title="Data mining">mine data</a> available in <a href="/wiki/Database" title="Database">databases</a> or <a href="/wiki/Web_directory" title="Web directory">open directories</a>. Unlike <a href="/wiki/Web_directories" title="Web directories" class="mw-redirect">web directories</a>, which are maintained only by human editors, search engines also maintain <a href="/wiki/Real-time_computing" title="Real-time computing">real-time</a> information by running an <a href="/wiki/Algorithm" title="Algorithm">algorithm</a> on a <a href="/wiki/Web_crawler" title="Web crawler">web crawler</a>.</p>
<table id="toc" class="toc">
<tr>
<td>
<div id="toctitle">
<h2>Contents</h2>
</div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="#History"><span class="tocnumber">1</span> <span class="toctext">History</span></a></li>
<li class="toclevel-1 tocsection-2"><a href="#How_web_search_engines_work"><span class="tocnumber">2</span> <span class="toctext">How web search engines work</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="#Market_share"><span class="tocnumber">3</span> <span class="toctext">Market share</span></a></li>
<li class="toclevel-1 tocsection-4"><a href="#Search_engine_bias"><span class="tocnumber">4</span> <span class="toctext">Search engine bias</span></a></li>
<li class="toclevel-1 tocsection-5"><a href="#Customized_results_and_filter_bubbles"><span class="tocnumber">5</span> <span class="toctext">Customized results and filter bubbles</span></a></li>
<li class="toclevel-1 tocsection-6"><a href="#See_also"><span class="tocnumber">6</span> <span class="toctext">See also</span></a></li>
<li class="toclevel-1 tocsection-7"><a href="#References"><span class="tocnumber">7</span> <span class="toctext">References</span></a></li>
<li class="toclevel-1 tocsection-8"><a href="#Further_reading"><span class="tocnumber">8</span> <span class="toctext">Further reading</span></a></li>
<li class="toclevel-1 tocsection-9"><a href="#External_links"><span class="tocnumber">9</span> <span class="toctext">External links</span></a></li>
</ul>
</td>
</tr>
</table>
<h2><span class="editsection">[<a href="/w/index.php?title=Web_search_engine&amp;action=edit&amp;section=1" title="Edit section: History">edit</a>]</span> <span class="mw-headline" id="History">History</span></h2>
<table class="bordered infobox">
<tr>
<th colspan="3">Timeline (<a href="/wiki/List_of_search_engines" title="List of search engines">full list</a>)</th>
</tr>
<tr>
<th>Year</th>
<th>Engine</th>
<th>Current status</th>
</tr>
<tr>
<td rowspan="2">1993</td>
<td><a href="/wiki/W3Catalog" title="W3Catalog">W3Catalog</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Aliweb" title="Aliweb">Aliweb</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td rowspan="3">1994</td>
<td><a href="/wiki/WebCrawler" title="WebCrawler">WebCrawler</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, Aggregator</td>
</tr>
<tr>
<td><a href="/wiki/Go.com" title="Go.com">Go.com</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, Yahoo Search</td>
</tr>
<tr>
<td><a href="/wiki/Lycos" title="Lycos">Lycos</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td rowspan="6">1995</td>
<td><a href="/wiki/AltaVista" title="AltaVista">AltaVista</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, Yahoo Search</td>
</tr>
<tr>
<td><a href="/wiki/Daum_Communications" title="Daum Communications">Daum</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Magellan_(search_engine)" title="Magellan (search engine)" class="mw-redirect">Magellan</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Excite" title="Excite">Excite</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/SAPO_(company)" title="SAPO (company)">SAPO</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Yahoo!" title="Yahoo!">Yahoo!</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, Launched as a directory</td>
</tr>
<tr>
<td rowspan="4">1996</td>
<td><a href="/wiki/Dogpile" title="Dogpile">Dogpile</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, Aggregator</td>
</tr>
<tr>
<td><a href="/wiki/Inktomi_(company)" title="Inktomi (company)" class="mw-redirect">Inktomi</a></td>
<td>Acquired by Yahoo!</td>
</tr>
<tr>
<td><a href="/wiki/HotBot" title="HotBot">HotBot</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active (lycos.com)</td>
</tr>
<tr>
<td><a href="/wiki/Ask.com" title="Ask.com">Ask Jeeves</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active (rebranded ask.com)</td>
</tr>
<tr>
<td rowspan="2">1997</td>
<td><a href="/wiki/Northern_Light_Group" title="Northern Light Group">Northern Light</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Yandex" title="Yandex">Yandex</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td rowspan="3">1998</td>
<td><a href="/w/index.php?title=Goto_Search&amp;action=edit&amp;redlink=1" class="new" title="Goto Search (page does not exist)">Goto</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Google_Search" title="Google Search">Google</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/MSN_Search" title="MSN Search" class="mw-redirect">MSN Search</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active as Bing</td>
</tr>
<tr>
<td rowspan="5">1999</td>
<td><a href="/wiki/AlltheWeb" title="AlltheWeb">AlltheWeb</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive (URL redirected to Yahoo!)</td>
</tr>
<tr>
<td><a href="/wiki/GenieKnows" title="GenieKnows">GenieKnows</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, rebranded Yellowee.com</td>
</tr>
<tr>
<td><a href="/wiki/Naver" title="Naver">Naver</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Teoma" title="Teoma">Teoma</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Vivisimo" title="Vivisimo">Vivisimo</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td rowspan="2">2000</td>
<td><a href="/wiki/Baidu" title="Baidu">Baidu</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Exalead" title="Exalead">Exalead</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td>2002</td>
<td><a href="/wiki/Inktomi_(company)" title="Inktomi (company)" class="mw-redirect">Inktomi</a></td>
<td>Acquired by Yahoo!</td>
</tr>
<tr>
<td>2003</td>
<td><a href="/wiki/Info.com" title="Info.com">Info.com</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td rowspan="3">2004</td>
<td><a href="/wiki/Yahoo!_Search" title="Yahoo! Search">Yahoo! Search</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, Launched own web search<br />
(see Yahoo! Directory, 1995)</td>
</tr>
<tr>
<td><a href="/wiki/A9.com" title="A9.com">A9.com</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Sogou.com" title="Sogou.com">Sogou</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td rowspan="4">2005</td>
<td><a href="/wiki/AOL_Search" title="AOL Search" class="mw-redirect">AOL Search</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Ask.com" title="Ask.com">Ask.com</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/GoodSearch" title="GoodSearch">GoodSearch</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/SearchMe" title="SearchMe">SearchMe</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td rowspan="6">2006</td>
<td><a href="/wiki/Wikiseek" title="Wikiseek">wikiseek</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Quaero" title="Quaero">Quaero</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Ask.com" title="Ask.com">Ask.com</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Live_Search" title="Live Search" class="mw-redirect">Live Search</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active as Bing, Launched as<br />
rebranded MSN Search</td>
</tr>
<tr>
<td><a href="/wiki/ChaCha_(search_engine)" title="ChaCha (search engine)">ChaCha</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Guruji.com" title="Guruji.com">Guruji.com</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td rowspan="4">2007</td>
<td><a href="/wiki/Wikiseek" title="Wikiseek">wikiseek</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Sproose" title="Sproose">Sproose</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Wikia_Search" title="Wikia Search">Wikia Search</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Blackle.com" title="Blackle.com" class="mw-redirect">Blackle.com</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td rowspan="7">2008</td>
<td><a href="/wiki/Powerset_(company)" title="Powerset (company)">Powerset</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive (redirects to Bing)</td>
</tr>
<tr>
<td><a href="/wiki/Picollator" title="Picollator">Picollator</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Viewzi" title="Viewzi">Viewzi</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Boogami" title="Boogami">Boogami</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/LeapFish" title="LeapFish">LeapFish</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Forestle" title="Forestle">Forestle</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive (redirects to Ecosia)</td>
</tr>
<tr>
<td><a href="/wiki/DuckDuckGo" title="DuckDuckGo">DuckDuckGo</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td rowspan="4">2009</td>
<td><a href="/wiki/Bing" title="Bing">Bing</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, Launched as<br />
rebranded Live Search</td>
</tr>
<tr>
<td><a href="/wiki/Yebol" title="Yebol">Yebol</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Mugurdy" title="Mugurdy">Mugurdy</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive due to a lack of funding</td>
</tr>
<tr>
<td><a href="/wiki/Goby_Inc." title="Goby Inc." class="mw-redirect">Goby</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td rowspan="4">2010</td>
<td><a href="/wiki/Blekko" title="Blekko">Blekko</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Cuil" title="Cuil">Cuil</a></td>
<td style="background: #FF9090; color: black; vertical-align: middle; text-align: center;" class="inactive table-siteinactive">Inactive</td>
</tr>
<tr>
<td><a href="/wiki/Yandex" title="Yandex">Yandex</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, Launched global<br />
(English) search</td>
</tr>
<tr>
<td><a href="/wiki/Yummly" title="Yummly">Yummly</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td rowspan="2">2011</td>
<td><a href="/w/index.php?title=Interred_educational_search_engine&amp;action=edit&amp;redlink=1" class="new" title="Interred educational search engine (page does not exist)">Interred</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active as Interredu</td>
</tr>
<tr>
<td><a href="/wiki/Yandex" title="Yandex">Yandex</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, Launched Turkey search</td>
</tr>
<tr>
<td rowspan="3">2012</td>
<td><a href="/wiki/Volunia" title="Volunia">Volunia</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/w/index.php?title=Interredu&amp;action=edit&amp;redlink=1" class="new" title="Interredu (page does not exist)">Interredu</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active</td>
</tr>
<tr>
<td><a href="/wiki/Open_Drive" title="Open Drive">Open Drive</a></td>
<td style="background: #90FF90; color: black; vertical-align: middle; text-align: center;" class="active table-siteactive">Active, <a href="/wiki/Cloud_storage" title="Cloud storage">cloud</a> file search</td>
</tr>
</table>
<p>During the early development of the web, there was a list of <a href="/wiki/Webserver" title="Webserver" class="mw-redirect">webservers</a> edited by <a href="/wiki/Tim_Berners-Lee" title="Tim Berners-Lee">Tim Berners-Lee</a> and hosted on the <a href="/wiki/CERN" title="CERN">CERN</a> webserver. One historical snapshot from 1992 remains.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span>[</span>1<span>]</span></a></sup> As more webservers went online the central list could not keep up. On the <a href="/wiki/National_Center_for_Supercomputing_Applications" title="National Center for Supercomputing Applications">NCSA</a> site new servers were announced under the title "What's New!"<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span>[</span>2<span>]</span></a></sup></p>
<p>The very first tool used for searching on the Internet was <a href="/wiki/Archie_search_engine" title="Archie search engine">Archie</a>.<sup id="cite_ref-LeidenUnivSE_3-0" class="reference"><a href="#cite_note-LeidenUnivSE-3"><span>[</span>3<span>]</span></a></sup> The name stands for "archive" without the "v". It was created in 1990 by <a href="/wiki/Alan_Emtage" title="Alan Emtage">Alan Emtage</a>, Bill Heelan and J. Peter Deutsch, computer science students at <a href="/wiki/McGill_University" title="McGill University">McGill University</a> in <a href="/wiki/Montreal" title="Montreal">Montreal</a>. The program downloaded the directory listings of all the files located on public anonymous FTP (<a href="/wiki/File_Transfer_Protocol" title="File Transfer Protocol">File Transfer Protocol</a>) sites, creating a searchable database of file names; however, Archie did not index the contents of these sites since the amount of data was so limited it could be readily searched manually.</p>
<p>The rise of <a href="/wiki/Gopher_(protocol)" title="Gopher (protocol)">Gopher</a> (created in 1991 by <a href="/wiki/Mark_McCahill" title="Mark McCahill" class="mw-redirect">Mark McCahill</a> at the <a href="/wiki/University_of_Minnesota" title="University of Minnesota">University of Minnesota</a>) led to two new search programs, <a href="/wiki/Veronica_(computer)" title="Veronica (computer)" class="mw-redirect">Veronica</a> and <a href="/wiki/Jughead_(computer)" title="Jughead (computer)" class="mw-redirect">Jughead</a>. Like Archie, they searched the file names and titles stored in Gopher index systems. Veronica (<i>V</i>ery <i>E</i>asy <i>R</i>odent-<i>O</i>riented <i>N</i>et-wide <i>I</i>ndex to <i>C</i>omputerized <i>A</i>rchives) provided a keyword search of most Gopher menu titles in the entire Gopher listings. Jughead (<i>J</i>onzy's <i>U</i>niversal <i>G</i>opher <i>H</i>ierarchy <i>E</i>xcavation <i>A</i>nd <i>D</i>isplay) was a tool for obtaining menu information from specific Gopher servers. While the name of the search engine "Archie" was not a reference to the <a href="/wiki/Archie_Comics" title="Archie Comics">Archie comic book</a> series, "<a href="/wiki/Veronica_Lodge" title="Veronica Lodge">Veronica</a>" and "<a href="/wiki/Jughead_Jones" title="Jughead Jones">Jughead</a>" are characters in the series, thus referencing their predecessor.</p>
<p>In the summer of 1993, no search engine existed for the web, though numerous specialized catalogues were maintained by hand. <a href="/wiki/Oscar_Nierstrasz" title="Oscar Nierstrasz">Oscar Nierstrasz</a> at the <a href="/wiki/University_of_Geneva" title="University of Geneva">University of Geneva</a> wrote a series of <a href="/wiki/Perl" title="Perl">Perl</a> scripts that periodically mirrored these pages and rewrote them into a standard format. This formed the basis for <a href="/wiki/W3Catalog" title="W3Catalog">W3Catalog</a>, the web's first primitive search engine, released on September 2, 1993.<sup id="cite_ref-Announcement_html_4-0" class="reference"><a href="#cite_note-Announcement_html-4"><span>[</span>4<span>]</span></a></sup></p>
<p>In June 1993, Matthew Gray, then at <a href="/wiki/Massachusetts_Institute_of_Technology" title="Massachusetts Institute of Technology">MIT</a>, produced what was probably the first <a href="/wiki/Web_robot" title="Web robot" class="mw-redirect">web robot</a>, the <a href="/wiki/Perl" title="Perl">Perl</a>-based <a href="/wiki/World_Wide_Web_Wanderer" title="World Wide Web Wanderer">World Wide Web Wanderer</a>, 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 <a href="/wiki/Aliweb" title="Aliweb">Aliweb</a> appeared in November 1993. Aliweb did not use a <a href="/wiki/Web_robot" title="Web robot" class="mw-redirect">web robot</a>, but instead depended on being notified by website administrators of the existence at each site of an index file in a particular format.</p>
<p><a href="/wiki/JumpStation" title="JumpStation">JumpStation</a> (released in December 1993<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span>[</span>5<span>]</span></a></sup>) used a <a href="/wiki/Web_crawler" title="Web crawler">web robot</a> to find web pages and to build its index, and used a <a href="/wiki/Web_form" title="Web form" class="mw-redirect">web form</a> as the interface to its query program. It was thus the first 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 pages the crawler encountered.</p>
<p>One of the first "all text" crawler-based search engines was <a href="/wiki/WebCrawler" title="WebCrawler">WebCrawler</a>, which came out in 1994. Unlike its predecessors, it allowed users to search for any word in any webpage, which has become the standard for all major search engines since. It was also the first one widely known by the public. Also in 1994, <a href="/wiki/Lycos" title="Lycos">Lycos</a> (which started at <a href="/wiki/Carnegie_Mellon_University" title="Carnegie Mellon University">Carnegie Mellon University</a>) was launched and became a major commercial endeavor.</p>
<p>Soon after, many search engines appeared and vied for popularity. These included <a href="/wiki/Magellan_(search_engine)" title="Magellan (search engine)" class="mw-redirect">Magellan</a>, <a href="/wiki/Excite" title="Excite">Excite</a>, <a href="/wiki/Infoseek" title="Infoseek">Infoseek</a>, <a href="/wiki/Inktomi_(company)" title="Inktomi (company)" class="mw-redirect">Inktomi</a>, <a href="/wiki/Northern_Light_Group" title="Northern Light Group">Northern Light</a>, and <a href="/wiki/AltaVista" title="AltaVista">AltaVista</a>. <a href="/wiki/Yahoo!" title="Yahoo!">Yahoo!</a> was among the most popular ways for people to find web pages of interest, but its search function operated on its <a href="/wiki/Web_directory" title="Web directory">web directory</a>, rather than its full-text copies of web pages. Information seekers could also browse the directory instead of doing a keyword-based search.</p>
<p>Google adopted the idea of selling search terms in 1998, from a small search engine company named <i>goto.com</i>. This move had a significant effect on the SE business, which went from struggling to one of the most profitable businesses in the internet.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span>[</span>6<span>]</span></a></sup></p>
<p>In 1996, <a href="/wiki/Netscape" title="Netscape">Netscape</a> 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.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span>[</span>7<span>]</span></a></sup><sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span>[</span>8<span>]</span></a></sup></p>
<p>Search engines were also known as some of the brightest stars in the Internet investing frenzy that occurred in the late 1990s.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span>[</span>9<span>]</span></a></sup> Several companies entered the market spectacularly, receiving record gains during their <a href="/wiki/Initial_public_offering" title="Initial public offering">initial public offerings</a>. 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 <a href="/wiki/Dot-com_bubble" title="Dot-com bubble">dot-com bubble</a>, a speculation-driven market boom that peaked in 1999 and ended in 2001.</p>
<p>Around 2000, <a href="/wiki/Google_Search" title="Google Search">Google's search engine</a> rose to prominence.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span>[</span>10<span>]</span></a></sup> The company achieved better results for many searches with an innovation called <a href="/wiki/PageRank" title="PageRank">PageRank</a>. This <a href="/wiki/Iterative_algorithm" title="Iterative algorithm" class="mw-redirect">iterative algorithm</a> 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. Google also maintained a minimalist interface to its search engine. In contrast, many of its competitors embedded a search engine in a <a href="/wiki/Web_portal" title="Web portal">web portal</a>.</p>
<p>By 2000, Yahoo! was providing search services based on Inktomi's search engine. Yahoo! acquired Inktomi in 2002, and <a href="/wiki/Overture" title="Overture">Overture</a> (which owned <a href="/wiki/AlltheWeb" title="AlltheWeb">AlltheWeb</a> 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.</p>
<p>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 <a href="/wiki/Looksmart" title="Looksmart" class="mw-redirect">Looksmart</a>, blended with results from Inktomi. For a short time in 1999, MSN Search used results from AltaVista were instead. In 2004, <a href="/wiki/Microsoft" title="Microsoft">Microsoft</a> began a transition to its own search technology, powered by its own <a href="/wiki/Web_crawler" title="Web crawler">web crawler</a> (called <a href="/wiki/Msnbot" title="Msnbot">msnbot</a>).</p>
<p>Microsoft's rebranded search engine, <a href="/wiki/Bing" title="Bing">Bing</a>, was launched on June 1, 2009. On July 29, 2009, Yahoo! and Microsoft finalized a deal in which <a href="/wiki/Yahoo!_Search" title="Yahoo! Search">Yahoo! Search</a> would be powered by Microsoft Bing technology.</p>
<p>In 2012, following the April 24 release of <a href="/wiki/Google_Drive" title="Google Drive">Google Drive</a>, Google released the <a href="/wiki/Software_release_life_cycle#Beta" title="Software release life cycle">Beta</a> version of <a rel="nofollow" class="external text" href="http://opendrive.mcommulticartes.com/start">Open Drive</a> (available as a <a rel="nofollow" class="external text" href="https://chrome.google.com/webstore/#detail/open-drive/biagdapeolcddppdgcocjkdjfhlodegf">Chrome app</a>) to enable the search of files in <a href="/wiki/Cloud_storage" title="Cloud storage">the cloud</a> that are publicly shared.</p>
<h2><span class="editsection">[<a href="/w/index.php?title=Web_search_engine&amp;action=edit&amp;section=2" title="Edit section: How web search engines work">edit</a>]</span> <span class="mw-headline" id="How_web_search_engines_work">How web search engines work</span></h2>
<table class="metadata plainlinks ambox ambox-content ambox-Original_research" style="">
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<td class="mbox-text" style=""><span class="mbox-text-span">This section <b>may contain <a href="/wiki/Wikipedia:No_original_research" title="Wikipedia:No original research">original research</a></b>. <span class="hide-when-compact">Please <a class="external text" href="//en.wikipedia.org/w/index.php?title=Web_search_engine&amp;action=edit">improve it</a> by <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verifying</a> the claims made and adding <a href="/wiki/Wikipedia:References" title="Wikipedia:References" class="mw-redirect">references</a>. Statements consisting only of original research may be removed.</span> <small><i>(October 2012)</i></small> </span></td>
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</table>
<table class="metadata plainlinks ambox ambox-content ambox-Unreferenced" style="">
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<div style="width: 52px;"><a href="/wiki/File:Question_book-new.svg" class="image"><img alt="Question book-new.svg" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" width="50" height="39" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" /></a></div>
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<td class="mbox-text" style=""><span class="mbox-text-span">This section <b>does not <a href="/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources">cite</a> any <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">references or sources</a></b>. <span class="hide-when-compact">Please help improve this section by <a href="/wiki/Help:Introduction_to_referencing/1" title="Help:Introduction to referencing/1">adding citations to reliable sources</a>. Unsourced material may be challenged and <a href="/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>.</span> <small><i>(October 2012)</i></small> </span></td>
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<p>A search engine operates in the following order:</p>
<ol>
<li><a href="/wiki/Web_crawling" title="Web crawling" class="mw-redirect">Web crawling</a></li>
<li><a href="/wiki/Index_(search_engine)" title="Index (search engine)" class="mw-redirect">Indexing</a></li>
<li><a href="/wiki/Web_search_query" title="Web search query">Searching</a><sup id="cite_ref-Jawadekar2011_11-0" class="reference"><a href="#cite_note-Jawadekar2011-11"><span>[</span>11<span>]</span></a></sup></li>
</ol>
<p>Web search engines work by storing information about many web pages, which they retrieve from the <a href="/wiki/HTML" title="HTML">HTML</a> itself. These pages are retrieved by a <a href="/wiki/Web_crawler" title="Web crawler">Web crawler</a> (sometimes also known as a spider) � an automated Web browser which follows every link on the site. Exclusions can be made by the use of <a href="/wiki/Robots.txt" title="Robots.txt" class="mw-redirect">robots.txt</a>. The contents of each page are then analyzed to determine how it should be <a href="/wiki/Search_engine_indexing" title="Search engine indexing">indexed</a> (for example, words can be extracted from the titles, page content, headings, or special fields called <a href="/wiki/Meta_tags" title="Meta tags" class="mw-redirect">meta tags</a>). Data about web pages are stored in an index database for use in later queries. A query can be a single word. The index helps find information as quickly as possible.<sup id="cite_ref-Jawadekar2011_11-1" class="reference"><a href="#cite_note-Jawadekar2011-11"><span>[</span>11<span>]</span></a></sup> Some search engines, such as <a href="/wiki/Google" title="Google">Google</a>, store all or part of the source page (referred to as a <a href="/wiki/Web_cache" title="Web cache">cache</a>) as well as information about the web pages, whereas others, such as <a href="/wiki/AltaVista" title="AltaVista">AltaVista</a>, store every word of every page they find.<sup class="Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources from November 2012">citation needed</span></a></i>]</sup> This cached page always holds the actual search text since it is the one that was actually indexed, so it can be very useful when the content of the current page has been updated and the search terms are no longer in it.<sup id="cite_ref-Jawadekar2011_11-2" class="reference"><a href="#cite_note-Jawadekar2011-11"><span>[</span>11<span>]</span></a></sup> This problem might be considered a mild form of <a href="/wiki/Linkrot" title="Linkrot" class="mw-redirect">linkrot</a>, and Google's handling of it increases <a href="/wiki/Usability" title="Usability">usability</a> by satisfying <a href="/wiki/User_expectations" title="User expectations">user expectations</a> that the search terms will be on the returned webpage. This satisfies the <a href="/wiki/Principle_of_least_astonishment" title="Principle of least astonishment">principle of least astonishment</a>, since the user normally expects that the search terms will be on the returned pages. Increased search relevance makes these cached pages very useful, even beyond the fact that they may contain data that may no longer be available elsewhere.<sup class="Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources from November 2012">citation needed</span></a></i>]</sup></p>
<div class="thumb tright">
<div class="thumbinner" style="width:222px;"><a href="/wiki/File:WebCrawlerArchitecture.svg" class="image"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/WebCrawlerArchitecture.svg/220px-WebCrawlerArchitecture.svg.png" width="220" height="168" class="thumbimage" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/WebCrawlerArchitecture.svg/330px-WebCrawlerArchitecture.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/df/WebCrawlerArchitecture.svg/440px-WebCrawlerArchitecture.svg.png 2x" /></a>
<div class="thumbcaption">
<div class="magnify"><a href="/wiki/File:WebCrawlerArchitecture.svg" class="internal" title="Enlarge"><img src="//bits.wikimedia.org/static-1.21wmf8/skins/common/images/magnify-clip.png" width="15" height="11" alt="" /></a></div>
High-level architecture of a standard Web crawler</div>
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<p>When a user enters a <a href="/wiki/Web_search_query" title="Web search query">query</a> into a search engine (typically by using <a href="/wiki/Keyword_(Internet_search)" title="Keyword (Internet search)" class="mw-redirect">keywords</a>), the engine examines its <a href="/wiki/Inverted_index" title="Inverted index">index</a> and provides a listing of best-matching web pages according to its criteria, usually with a short summary containing the document's title and sometimes parts of the text. The index is built from the information stored with the data and the method by which the information is indexed.<sup id="cite_ref-Jawadekar2011_11-3" class="reference"><a href="#cite_note-Jawadekar2011-11"><span>[</span>11<span>]</span></a></sup> As early as 2007 the Google.com search engine has allowed one to search by date by clicking 'Show search tools' in the leftmost column of the initial search results page, and then selecting the desired date range.<sup class="Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources from November 2012">citation needed</span></a></i>]</sup> Most search engines support the use of the <a href="/wiki/Boolean_operators" title="Boolean operators" class="mw-redirect">boolean operators</a> AND, OR and NOT to further specify the <a href="/wiki/Web_search_query" title="Web search query">search query</a>. 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 <a href="/wiki/Proximity_search_(text)" title="Proximity search (text)">proximity search</a>, which allows users to define the distance between keywords.<sup id="cite_ref-Jawadekar2011_11-4" class="reference"><a href="#cite_note-Jawadekar2011-11"><span>[</span>11<span>]</span></a></sup> There is also concept-based searching where the research involves using statistical analysis on pages containing the words or phrases you search for. As well, natural language queries allow the user to type a question in the same form one would ask it to a human. A site like this would be ask.com.<sup class="Tem…
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