MediaWiki is the name of the software that runs all of the Wikimedia projects and many more].  MediaWiki was released in 2003.  It is free server-based software which is licensed under the GNU General Public License (GPL).  The software is licensed under the GPL. This means it is free content, or open source.

MediaWiki is designed to be run on a large web server farm for a website that gets millions of hits per day.  MediaWiki is a very powerful, scalable software and a feature-rich wiki implementation, that uses PHP to process and display data stored in its MySQL database.  Pages use MediaWiki's Wikitext format, so that users without knowledge of XHTML or CSS can edit them easily.

When a user submits an edit to a page, MediaWiki writes it to the database, but without deleting the previous versions of the page, thus allowing easy reverts in case of vandalism or spamming. MediaWiki can manage image and multimedia files, too, which are stored in the filesystem. For large wikis with lots of users, MediaWiki supports caching and can be easily coupled with Squid proxy server software.

All Wikimedia projects run on MediaWiki version  .

Usage 

Because MediaWiki is flexible, many websites that want people to contribute information use MediaWiki rather than other types of wiki software. Those operated by Fandom are among them.

There are also some websites that use MediaWiki as a content management system.

Extensions 
In MediaWiki, a system administrator can choose to install extensions which are provided on the main MediaWiki website. Some are from the MediaWiki developers, while others are from programmers from all around the world.

Most extensions can be download from Wikimedia's Subversion repository. However, there are some other extensions that other people host themselves.

Some extensions had been added to the main software along the development of MediaWiki. For example, the Makesysop extension is an extension to promote a user into an administrator or a bureaucrat.

There were a total of 2124 extensions as of October 4, 2013.

Namespaces 
In the default installation of MediaWiki, the software has 17 namespaces(18 actually, but one does not have a namespace), namely:
 Article (No namespace, like this page)
 Talk – for main namespace talk page
 User – the user page, also from Special:MyPage
 User talk – the user talk page, also from Special:MyTalk
 Project – The project namespace (like on this wiki, is Wikipedia)
 Project talk – The project page talk page
 File – Page for images and sounds
 File talk – Talk about the media
 MediaWiki – Software pages, can only be changed from an administrator
 MediaWiki talk – Talk about the software page, anyone can write in this namespace
 Template – for templates
 Template talk – talk about the template
 Help – Help pages (like Help:Contents)
 Help talk – talk about the help page
 Category - Categorising pages
 Category talk – talk about the category
 Special – Special pages of the MediaWiki software
 Media – Namespace to directly link to the file

Additional namespaces can be added using the settings file from the installation of MediaWiki.

Bugs 
As MediaWiki is a complex software, there would always be bugs in the software, especially for new extensions. Therefore, Wikimedia has created a Bugzilla website for people who see a bug to tell the developers of MediaWiki.

Some extensions of MediaWiki use the Wikimedia Bugzilla, while some just use the talk pages of the extension page.

Skins 

Users can customize MediaWiki for different appearance. They may use one of the several "skins". At different times different skins have been default. For example, Wikipedia once used Monobook before adopting the new Vector skin in version 1.16.

A survey done by Wikimedia showed that more people prefer the Vector skin.

More information 
More information about the software:

 Main MediaWiki website
 MediaWiki on Meta Wiki
 MediaWiki User's Guide on Meta Wiki
 PHP script FAQ
 PHP script automatic wikification (former feature)
 How to become a MediaWiki hacker (installation advice)

References

Other websites
 Wikitech-L mailing list (technical discussions regarding the development)
 Sites using MediaWiki
 Sourceforge: MediaWiki Project page Now changed to MediaWiki.org.
 Sourceforge: MediaWiki Bug reports Now changed to Wikimedia Bugzilla.
 Sourceforge: MediaWiki Feature requests Now changed to Wikimedia Bugzilla.
 Translatewiki.net – The place to translate MediaWiki messages.

Wiki software
Wikimedia
Websites established in 2002