Manual:$wgExtensionDirectory

Server URLs and file paths: $wgExtensionDirectory
The file system path to the extensions directory.
Introduced in version:1.25.0 (Gerrit change 209216; git #cf2678e2)
Removed in version:still in use
Allowed values:(relative path)
Default value:null (1.38+)
"{$IP }/extensions" (1.25-1.37)

DetailsEdit

The file system path to the extensions directory (relative path). This controls where MediaWiki will look for extensions on the server itself.

This is set to "{$IP}/extensions" by Setup.php before loading local settings.
Ignored when the exact path to a particular template's .json configuration file is given to the wfLoadTemplate() function.
Example: wfLoadTemplate( 'TemplateName', '/path/to/TemplateName/template.json' );

See alsoEdit