Mu-plugins (also known as ‘must use’ plugins) are the plugins located in the “mu-plugins” folder; these are activated by default affecting all sites on a WordPress Multisite installation.

You can download mu-plugins from WPMU DEV plugins — this is the largest collection of mu-plugins in one place and are supported through the WPMU DEV forum.

Setting up your mu-plugins folder

Before you can install mu-plugins on your WordPress Multisite installation you need to create a mu-plugins folder as follows:

1.  Create your mu-plugins folder in wp-content using FileZilla by clicking on right clicking and selecting Create directory.
2.  Add the directory name mu-plugins and click OK.

3.  Right click on your mu-plugins directory and select file permissions.
4.  Set the file permission to 755 and click OK.

Installing mu-plugins

Alternatively, refer to our video tutorial on installing mu-plugins using FTP.

If you are using Multi-DB:

  • You need to add the global table lines to db-config.php BEFORE installing the plugin or running the sql.txt
  • The plugin’s install file will specify what lines to add to your db-config.php if using multi-db:

Install the mu-plugin as follows:

1. Download the mu-plugin
2. Unzip the file to extract all files into a folder on your hard drive

  • Please note WPMU DEV plugins are contained within a zip file inside the folder you unzipped and you will need to unzip this file also.
  • For example, with Add New Users you need to also unzip add-new-users-1.0.2 zip

3. Read carefully all installation instructions for the plugin — some plugins involve uploading php files and folders to a range of different locations.

  • Make sure you read these instructions carefully
  • Many mu-plugins require additional steps to install other than those explained below.
  • If you don’t follow these instructions correctly the plugin won’t work and may cause problems on your installation.

With WPMU DEV plugins you need to carefully read:

  1. The readme file
  2. The install file
  3. Most important — refer to the installation page where you downloaded the plugin.  The installation page contains detailed step-by-step instructions for installing plus instructions for how to use the plugin.  For example, this is the installation page for Add New Users.

4. Launch FileZilla
5. Enter your domain name, your username and password. NOTE: the same username and password that you use to log into your cPanel.
6. Click Quickconnect

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Installing MU Plugins from Incsub on Vimeo.

See Next: Running a SQL code on your WPMU database