Extensions are installable packages which give CiviCRM new functionality, and this directory provides a centralized list of extensions which the CiviCRM community has created.
This listing displays CiviCRM extensions that work on all Content Management Systems (CMS). You can also browse directories of plugins or modules that are made specifically for Backdrop, Drupal, Joomla and WordPress. View newest extensions. There are also many more extensions in various stages of development available on CiviCRM's Gitlab.
Requires - CiviCRM 5.x, php 5.6
Credit : the Wikimedia Foundation
For example if it is installed on a CiviCRM system it will minify crm-menubar.css. If Stripe is installed it will minify stripe css/js.