WordPress: Must-Use Plugins?

A plugin that is uploaded to the “mu-plugins” folder is always activated by default and can not be accidentally deactivated by the user. It was originally created for multi-site blogs (as “multi-user” plugins that were active on all sites of a multi-site) but can now also be used for single sites.

MU-Plugins:

  • can not be deactivated
  • are always executed
  • can not use activation hooks
  • loaded before all other plugins (in alphabetical order)

Visit the documentation for more.