What free software powers Wikipedia and many other wikis?

MediaWiki is the free software that powers Wikipedia and many other wikis.

Wikipedia began in January 2001 using UseModWiki, but that Perl-based system soon proved limiting for a rapidly expanding encyclopedia. Magnus Manske developed a replacement in PHP, using a database-backed design. The new software went into service on Wikipedia in January 2002; the name MediaWiki was adopted later as a play on Wikimedia.

The software is maintained primarily by the Wikimedia Foundation and is released under the GNU General Public License. It stores page text, revision histories, links, accounts, and other data in databases, while extensions add features such as visual editing, spam controls, maps, and advanced search. Its architecture has been heavily optimized for Wikipedia-scale traffic.

A common mix-up is confusing MediaWiki with Wikimedia or Wikipedia. Wikipedia is the encyclopedia, Wikimedia is the foundation and project family, and MediaWiki is the software platform. MediaWiki also runs Wiktionary, Wikimedia Commons, Wikidata, Fandom wikis, and many private knowledge bases.