Thread:Project:Support desk/Does Visual Editor Extension Work At Mediawiki 1.21.1??/reply

As written on http://www.mediawiki.org/wiki/Extension:VisualEditor, "VisualEditor currently has dependencies on pre-release alpha versions of MediaWiki (as of July 2013, 1.22wmf4); if you want to install it, you should shell into your server and use git to download the very latest version"