Plugins are composed of PHP scripts that extend and expand the functionality of WordPress.

They work by enhancing existing WordPress features or adding new features.

There are two types of plugins:

1.  Regular plugins

  • These plugins are located in the “plugins” folder;
  • They can be activated and deactivated on a per site basis inside the dashboard via the Plugins page in the Site Admin dashboard.
  • They can be  Network Activated or Network Deactivated via the Plugins page in the Network Admin dashboard.

When a plugin is Network Activated that plugin is automatically activated network-wide and is available for use on all sites across the network.

If a plugin is ‘Network Activated’ it no longer appears in the Site Admin dashboard at all.  Only a Super Admin user is able to deactivate a ‘Network Activated’ plugin via the Plugins page in the Network Admin dashboard.

2.  mu-plugins

  • Stands for ‘must-use’ plugins. These are the plugins that are located in the “mu-plugins” folder.
  • Any plugins placed in the mu-plugins folder are automatically activated network wide.
  • Refer to Installing mu-plugins for more information.

Regular plugins and mu-plugins are located in separate folders on your WordPress Multisite.

Image of plugins folders

Your Default Plugins

WordPress and WordPress Multisite come with two default regular plugins installed:

  1. Akismet – a spam commenting service designed to reduce comment and pingback spam. It checks the content of a comment anonymously with an online server, to determine whether it is spam or not. Here’s how to configure and use Akismet
  2. Hello Dolly – adds a random lyric from “Hello, Dolly” to the top of your dashboard that changes as you navigate your admin panels

Things to know before installing plugins

While there are over 4,000 regular plugins most of these don’t work on WordPress Multisite sites and many have compatibility issues.

All WPMU DEV plugins are designed to be compatible with WordPress Multisite sites.

Make sure you check the plugin’s compatibility information before installing. The plugin may not have been updated for the version of WordPress you are using.

Plugins can be sourced through sites such as:

  1. WPMU DEV
  2. WordPress Plugins Directory
  3. WP Plugins

Whenever installing plugins on a WordPress Multisite install you should always:

  • Check the plugin’s compatibility information before installing. The plugin may not have been updated for the version of WordPress you are using
  • Thoroughly test each plugin (one at a time) by uploading it to your WordPress Multisite install and enabling it just for a test account
  • Activate the plugin on the test site, taking notes of any errors which occur
  • Immediately remove any plugins with bugs using FTP and only use them network wide once you have fixed all of their issues
  • Also, some plugins make changes to your database. Before installing any plugin that make dramatic changes, backup your database and files.

Important instructions when using WPMU DEV plugins

Most WPMU DEV plugins are now designed to be installed in the plugins folder.  Once uploaded you would normally Network Activate the plugin via the Plugins page in the Network Admin dashboard.

Read carefully all of the installation instructions for WPMU DEV plugins — some plugins involve uploading PHP files and folders to a range of different locations.

  • Make sure you read these instructions carefully
  • Some WPMU DEV plugins require additional steps to install and use
  • If you don’t follow these instructions correctly the plugin won’t work and may cause problems with your installation

See Next: Installing Regular Plugins on WordPress and WordPress Multisite