WordPress Multisite can work for someone with diverse interests and a handful of personal websites, a developer with a community of users, a big organization, or marketers with multiple niche sites. WordPress.com is probably the biggest Multisite installation out there, with millions of users. Edublogs.org is a success story for teachers, students, and campuses, with over a million blogs.

WP Multisite is integrated into “regular” WordPress, unlike earlier versions of WPMU (WordPress Multi-User), which required a separate, specialized version of WordPress. I didn’t jump on the bandwagon until a couple of years ago when Multisite was integrated into WordPress 3.0. Setting up Multisite requires only a little more effort than a single-site installation. If you like to make websites and play with new ideas for your sites, it’s a serious timesaver.

The advantages of WP Multisite are compelling:

  • Update WordPress once for all sites in a a WPMS network. Makes keeping up-to-date, and therefore more secure, quick and easy.
  • Run one daily database backup on the main site, and includes child site tables. Practically effortless with a set-and-forget plugin!.
  • Use your favorite themes with several sites. Some themes, such as Atahualpa (an excellent free theme) offer options for each child site, making it possible to have different header images, logos, colors, and layouts.
  • Ensure consistent graphical identity, styling and functionality for a group of related or branded sites by using the same theme and plugins.
  • Plugins can be network activated and updated from the Network Admin panel. Saves time and ensures that all sites have the latest versions. If all the child sites are your own, plugins can be individually installed when they aren’t needed on multiple sites.

WPMS has a few disadvantages, depending on how you use multiple sites:

  • Networked sites will have the same IP address. Remember that Domain Mapping does not change the numeric IP address. A large number of sites with the same IP could be evaluated by Google or other search engines as dodgy or less worthy than sites that have a dedicated IP address. Thanks to aggressive spammers and sleezy cookie-cutter sites, WPMU acquired a reputation that the rest of us have to transcend.
  • It’s possible to shoot yourself in the foot with Multisite if you mess up one of your themes, do bad things with unstable or incompatible plugins, or mess up your database.
  • It may be impossible to customize a theme the way you would like without changing it for all sites in your network. On the other hand, some customizations are desirable on all sites that use a particular theme.

There are some good tutorials on setting up WP Multisite. In spite of that, it’s possible to get stuck if some bit of information is left out of the instructions. Once you figure it out, it’s not rocket science after all.

Can You Do it Yourself?

If you are comfortable with WordPress and don’t mind working with a little code and settings, you can do this. Nevertheless, switching to Multisite is still a big change in direction. Server requirements, precautions, and the setup procedure are all clearly described in the Create A Network section of the WordPress Codex. Read it before doing anything else.

Before setting off, make sure your web hosting service doesn’t have any heartburn about using Multisite and supports wildcard subdomains. You will use the main domain of your hosting account for WordPress, which should be installed in the root directory, not in a separate folder. The first fork in the road will be to decide whether you will use subdomains or subdirectories for your networked sites. You can’t have both. Subdomains give you more flexibility because they can stay simple subdomains or be mapped as independent sites with their own domain names. Before configuring WordPress for Multisite, set up a wildcard subdomain on your web hosting account for the networked sites.

In order to see the Multisite option in WordPress, you must edit your wp-config.php file and add the line: define(‘WP_ALLOW_MULTISITE’, true);

After you do this, WordPress will guide you through the setup steps, which involve pasting edits to the wp-config.php file and the .htaccess file. If all goes well, you will see the Network Admin options when you log in again. These options used to be more visible, but they are now buried in the dropdown under “Howdy, YourName” in the top right-hand corner of the WP-Admin screen.

It’s possible to install WPMS on your home PC if you run XAMPP or WAMP and WordPress. I use it frequently to set up small staging sites or test themes. Everything is in subdirectories, not subdomains, of the localhost webroot. Very easy to setup and maintain.

Moving existing websites into Multisite takes attention to detail. For help, I found this post about combining multiple wordpress installs very helpful. It was written for WP 3.0, when Multisite was introduced, so a few things have changed, but it’s still a good resource. Another site that was extremely helpful was Otto’s WordPress 3.0: Multisite Domain-mapping Tutorial.