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.

  • 95 % of WPMU DEV plugins are now designed to be installed in the /wp-content/plugins/ folder on your site.  A few, however, like multi-DB, domain mapping, multi-domains, additional tags need to be installed in the /wp-content/mu-plugins/ folder
  • Always read carefully all installation instructions for the plugin because some plugins involve uploading PHP files and folders to a range of different locations.

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 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 which lines to add to your db-config.php if using multi-db.

Install the mu-plugin as follows:

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

3. Read all installation instructions for the plugin carefully – 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

About WPMU DEV plugins installation instructions

  • WPMU DEV plugins don’t include readme or install files.  You need to refer to the install page where you downloaded the plugin.
  • The installation page contains detailed step-by-step instructions for installing as well as instructions on how to use the plugin.
  • For example, this is the installation page for multi-domains.

4. Launch FileZilla
5. Enter your domain name, your username and password.
6. Click Quickconnect

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See Next: WPMU DEV Plugins Separated into Categories to Help Make Selecting Your Next Plugin Easier