Anextension lets you customise how MediaWiki looks and works.
While some extensions are maintained by MediaWiki developers, others were written by third-party developers. As a result, many have bugs, and they are not all guaranteed to be compatible with each other. Some are unmaintained; not all extensions work on all versions of MediaWiki. Use any extension, especially those tagged as insecure, at your own risk. If you are using an extension that requires patches to the core software, be sure to back up your database.This helps avoid the risk of breaking your wiki.
You can browseCategory:Extensions by category to see the full range of extensions that have already been written. For information on installing these extensions or writing your own, see below.
Only someone with administration access to the filesystem (and often the database too) on a server can install extensions for MediaWiki, but anyone can check which extensions are active on an instance of MediaWiki by accessing theSpecial:Version page. For example,these extensions are active in the English Wikipedia.
There are a number of ways of finding popular extensions.
The first set is those that arebundled with MediaWiki (a list that is reviewed regularly, and to which anyone cansuggest an addition).
Extensions that are downloaded from MediaWiki.org via theExtensionDistributor mechanism have some statistics gathered.The top 15 most downloaded extensions are listed atSpecial:ExtensionDistributor, and applicable extensions have their download count shown in their infobox.Note that these numbers do not account for alternate ways of installing extensions, such asvia Git orComposer.
A third option is to look atWikiApiary's counts of wikis that extensions are installed on.This has the advantage of representing actual installations and not just downloads (i.e. it queries the wiki's APIs), but it is also (as of 2023) not completely up to date.It also doesn't count installations on private wikis.
MediaWiki is ready to accept extensions just afterinstallation is finished. To add an extension follow these steps:
$IP/extensions/. A list of extensions stored in the WikimediaGit repository is located atgit:mediawiki/extensions. Some extensionsdon't use version control and are not recommended.LocalSettings.php file, add:wfLoadExtension('ExtensionName');
if(!$wgCommandLineMode){wfLoadExtension('ExtensionName');}
LocalSettings.php, you have to do this typicallyafter including the extension. Otherwise defaults defined in the extension will overwrite your settings.Some extensions require to be updated whenever you update MediaWiki, while others work with multiple versions. To upgrade to a new version of an extension:
extensions/ExtensionName directory with the new files. Do not remove the extension configuration present inLocalSettings.phpRemove the line fromLocalSettings.php with the extension name to uninstall it:
wfLoadExtension('ExtensionName');
MediaWiki core provides several ways for extensions to change the behavior and appearance of a wiki.Theseextension points give extensions flexibility to add features and functionality, such as displaying a special page or defining an API module.To get started, see theguide to developing extensions.Before writing a new extension, consider contributing to anexisting extension or helping with anunmaintained extension.