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If you have been testing out the beta of WordPress, and are new to the whole concept of multiple sites, you may have noted a lot of the wordpress-mu-specific plugins make reference to the mu-plugins folder.

This is not created by default. You must create it in the wp-content folder.

The “mu” does not stand for multi-user like it did for WPMU, it stands for “must-use” as any code placed in that folder will run without needing to be activated. An actual file has to be there; if all the files are in a subfolder, they will not be read.

You can now see the content of that folder in the backend, under the Plugins menu. When visiting, you’ll see a sub-item called “Must Use”, if you’ve created that folder and placed files within.


  1. Great, and super helpful explanation! I was wondering how the mu-plugins folder was going to fit in.

    Will Plugin Commander still be needed, or will this “activate plugin sitewide” be built-in?

  2. Just out of curiosity, when do these plugins load? Could I use them to affect the way the wordpress environment loads entirely, such as to change the database connections specified in wp-config.php?

  3. Hey there, I would also like to go and test wp 3.0. Is there a way to update from wpmu 2.9.2 to the wp 3.0 beta 1?

    I’ve installed the wp beta tester plugin, which just does not work for that unfortunately. And I don’t really want to do it manually since I fear I could do something wrong…


  4. This is a little off topic, but is the current version of Plugin Commander still needed in 2.9.2? (as I notice I have option in 2.9.2 package to enable or disable a plugin site-wide).