Skins {#skin}

Core Skins

MediaWiki includes four core skins:

Vector: The default skin. Introduced in the 1.16 release (2010), it has been set as the default in MediaWiki since the 1.17 release (2011), replacing Monobook.
Monobook: Named after the black-and-white photo of a book in the page background. Introduced in the 2004 release of 1.3, it had been the default skin since then, before being replaced by Vector.
Modern: An attractive blue/grey theme with sidebar and top bar. Derived from Monobook.
Cologne Blue: A lightweight skin with minimal formatting. The oldest of the currently bundled skins, largely rewritten in 2012 while keeping its appearance.

Legacy core skins

Several legacy skins were removed in the 1.22 release, as the burden of supporting them became too heavy to bear. Those were:

Standard (a.k.a. Classic): The old default skin written by Lee Crocker during the phase 3 rewrite, in 2002.
Nostalgia: A skin which looks like Wikipedia did in its first year (2001). This skin is now used for the old Wikipedia snapshot at https://nostalgia.wikipedia.org/
Chick: A lightweight Monobook skin with no sidebar. The sidebar links were given at the bottom of the page instead.
Simple: A lightweight skin with a simple white-background sidebar and no top bar.
MySkin: Essentially Monobook without the CSS. The idea was that it could be customised using user-specific or site-wide CSS (see below).

Custom CSS/JS

It is possible to customise the site CSS and JavaScript without editing any server-side source files. This is done by editing some pages on the wiki:

MediaWiki:Common.css for skin-independent CSS
MediaWiki:Common.js for skin-independent JavaScript
MediaWiki:Vector.css, MediaWiki:Monobook.css, etc. for skin-dependent CSS
MediaWiki:Vector.js, MediaWiki:Monobook.js, etc. for skin-dependent JavaScript

These can also be customised on a per-user basis, by editing User:<name>/vector.css, User:<name>/vector.js, etc.

Custom skins

Several custom skins are available as of 2019. List of all skins is available at MediaWiki.org.

Installing a skin requires adding its files in a subdirectory under skins/ and adding an appropriate wfLoadSkin line to LocalSettings.php, similarly to how extensions are installed.

You can then make that skin the default by adding:

php

$wgDefaultSkin = '<name>';

Or disable it entirely by removing the wfLoadSkin line. (User settings will not be lost if it's reenabled later.)

See https://www.mediawiki.org/wiki/Manual:Skinning for more information on writing new skins.

Legacy custom skins

Until MediaWiki 1.25 it used to be possible to just put a <name>.php file in MediaWiki's skins/ directory, which would be loaded and expected to contain the Skin<name> class. This way has always been discouraged because of its limitations (inability to add localisation messages, ResourceLoader modules, etc.) and awkwardness in managing such skins. For information on migrating skins using this old method, see https://www.mediawiki.org/wiki/Manual:Skin_autodiscovery.