WordPress MU Is Now WordPress Multisite: What It Is and How to Set It Up

WordPress MU (multi-user) was the separate edition of WordPress that let one installation run many blogs for many users. It no longer exists as a separate download: its features were merged into regular WordPress and renamed WordPress Multisite. If you searched for WordPress MU, this guide explains what Multisite is today, when it makes sense and how to switch it on.

Quick answer: WordPress MU was merged into WordPress 3.0 in 2010 and is now called WordPress Multisite. To use it, add define( ‘WP_ALLOW_MULTISITE’, true ); to wp-config.php, then go to Tools > Network Setup, choose subdomains or subdirectories and follow the steps. Multisite suits networks of related sites run by one team; separate installs are simpler for unrelated sites.

From WordPress MU to WordPress Multisite

When we covered WordPress MU in 2006, it was a separate download from the old mu.wordpress.org site, aimed at people who wanted to host blogs for others, the way WordPress.com does. It was harder to install and maintain than normal WordPress. Since WordPress 3.0 the same capability is built into every copy of WordPress, so there is nothing extra to download; you simply turn the network feature on.

What is WordPress Multisite?

WordPress Multisite lets one WordPress installation run a network of sites. All sites share the same WordPress files, plugins and themes, while each site has its own content, settings and users.

• Super Admin: manages the whole network, installs plugins and themes, and creates sites.
• Site admins: manage their own site’s content and settings.
• Shared users: one account can be added to several sites with different roles on each.

When to use WordPress Multisite

• A university, school or company with many department sites.
• A news group or brand with regional or language editions.
• An agency hosting many similar client sites that share one set of plugins.
• A blog network or community where users get their own site.

When separate installs are better

• Sites that need very different plugins or must be moved to different hosts later.
• Client sites where each client needs full admin control of their own plugins.
• Hosting plans that do not support Multisite. Check with your host first.

How to set up WordPress Multisite

The steps below follow the official WordPress guide to creating a network (external site). Take a full backup first.

1. Allow Multisite. Open wp-config.php and add this line above the “That’s all, stop editing” comment:

   define( 'WP_ALLOW_MULTISITE', true );

2. Deactivate all plugins while you set up the network.
3. Open Tools > Network Setup. This menu item appears after step 1.
4. Choose subdomains or subdirectories. Subdomains give sites addresses like site1.example.com; subdirectories give example.com/site1/. You can change later, but it is not easy.
5. Copy the code WordPress shows into wp-config.php and your server’s rewrite rules (.htaccess on Apache), then log in again.
6. Add sites from My Sites > Network Admin > Sites, and reactivate plugins network-wide or per site.

Tips for running a Multisite network

• Test plugins and themes on one site before network-activating them.
• Back up the whole network: all sites share one database.
• Subdomain networks usually need wildcard DNS and an SSL certificate that covers subdomains.
• Keep the number of network-activated plugins small, since every site loads them.

Building a community rather than separate sites? BuddyPress adds profiles, groups and activity streams to WordPress. For the story of a service that grew up around WordPress MU, see how WPMU DEV started.

FAQ

Is WordPress MU still available?

No. It was merged into WordPress 3.0 in 2010. The same features are now WordPress Multisite, included in every WordPress download.

Is WordPress Multisite free?

Yes. It is part of WordPress itself. You only need hosting that supports it.

Can I convert an existing site to Multisite?

Yes. Follow the setup steps above on your existing install. Your current site becomes the main site of the network. Back up first.

Subdomains or subdirectories: which is better?

Subdirectories are simpler to set up because they need no extra DNS. Subdomains suit sites that should feel more independent.