Manual:$wgStyleDirectory

Server URLs and file paths: $wgStyleDirectory
The file system path to the skins directory.
Introduced in version:	1.3.0
Removed in version:	Still in use
Allowed values:	(relative path)
Default value:	`null` (1.38+) `"{$IP }/skins"` (1.4-1.37) `"{$IP }/style"` (1.3)
Other settings: Alphabetical \| By function

Details

The file system path to the skins directory. This controls where MediaWiki will look for skin files on the server itself.

Set to "{$IP}/skins" by Setup.php before loading local settings.

Ignored when the exact path to a particular skin's .json configuration file is given to the wfLoadSkin() function.

Example: wfLoadSkin( 'Vector2', '/path/to/Vector2/skin.json' );