Manual:$wgLanguageCode

Details
The site language code is usually set automatically with the installer. List of languages codes can be found at  . The code should be in lower case and use hyphen as separator. Examples:,  ,  ,

This specifies which language your page content is in, and also provides the default language for your wiki's interface. While users can switch the language of interface messages in their 1>Special:MyLanguage/Help:Preferences|preferences, anonymous visitors will see the wiki's interface in the content language.  provides a way to auto-detect the language of anonymous users and let them choose their interface language without logging in.

Change existing users' language settings
You can change existing users' language settings with the  2>Special:MyLanguage/Manual:Maintenance scripts|maintenance script. They will still be able to change their settings back unless you disable that option (1>#Disable user selection of language|see below).

Disable user selection of language
If you want to have your wiki in a certain language and not allow users to change this setting, there is a new variable in 1.16 and above,  :