WordPress Multisite Reference: Must-Use Plugins Gets an Updated Codex Page

WordPress Multisite Reference: Must-Use Plugins Gets an Updated Codex Page

The mu-plugins directory was originally implemented in WPMU, which was merged in WordPress 3.0 and renamed to Multisite.

This directory is now also referred to as the Must-Use plugins directory and you can find a new codex page in the works at:


This page explains the basic features of the mu-plugins directory:

  • Always-on, no need to enable via admin and users cannot disable by accident.
  • Can be enabled simply by uploading files to the mu-plugins directory, without having to log in.
  • Loaded by PHP before normal plugins, meaning API hooks added in an mu-plugin apply to all other plugins even if they run hooked-functions in the global namespace.

It is important to bear in mind that the mu-plugins directory should only be used for plugins that have been written to be multi-use compatible. However, all WordPress sites are able to take advantage of autoloaded plugins, whether you have MU/Multisite enabled or not. Please note that you may need to create the directory itself, as it is not auto-generated by WordPress.

Another important thing to remember is that update notifications will not be shown for these plugins, so you’ll be responsible for finding out when these plugins can be updated.

If you’re considering adding a plugin to the mu-plugins directory, make sure to thoroughly check and test its compatibility before deploying on a live site.

More Helpful Resources…

If you have anything to add, please jump in and help to make the Must-Use Plugins page a better reference. You can also find quite a bit more information in our WordPress and WordPress Multisite Manual. The section titled: Introduction to Using Plugins on WordPress and WordPress Multisite is particularly useful and contains many practical tips for uploading and testing plugins in a multi-use environment. Make sure to bookmark these references for the next time you need them.