Extensions are distributed separately. Drop them into this directory and enable as per the extension's installation instructions. You can find a list of extensions and documentation at . If you are a developer, you might want to fetch the extension tree in another directory and make a symbolic link: mediawiki/extensions$ ln -s ../../extensions-trunk/FooBar Most extensions are available through Git: https://phabricator.wikimedia.org/diffusion/MEXT/ Please note that under POSIX systems (Linux...), parent of a symbolic path refers to the link source, NOT to the target! You should check the env variable MW_INSTALL_PATH in case the extension is not in the default location. The following code snippet lets you override the default path: $IP = getenv( 'MW_INSTALL_PATH' ); if( $IP === false ) { $IP = __DIR__ . '/../..'; } require_once "$IP/maintenance/Maintenance.php"; // a MediaWiki core file