Did you know that WordPress has the ability to run multiple websites from one installation of WordPress? This type of configuration is called WordPress Multisite.
In the past there were two versions of WordPress; standard WP that we all know and love and WordPress MU (Multi User) were distinct downloads. With the release of WordPress 3.x those two versions were brought together.
What Is Multisite?
After a making a couple of configuration changes, you can make your current installation of WordPress manage multiple WordPress sites. Each site will have it’s own content, users, plugins and themes.
The benefit is you only have one installation of WordPress to manage and maintain, a brilliant time saver for owners of multiple WordPress sites.
UPDATE June 2012: Video Tutoral
Feel free to read the whole blog post, but I’ve created a free video tutorial to show you how to build a multisite installation.
Making A Single Site Multisite
This post is an overview of multi site, so I’m not going to go into the technical details of configuring a network in this post (if there is enough demand I may setup a training session, leave a comment if you would like this type of session).
There is a very good tutorial over at WordPress.org which will take you through the process.
The first thing to consider before moving to MS is the question of compatibility. Not all themes and plugins will work on Multisite. Check with your theme and plugin suppliers to see if it is compatible first. For example my favourite back plugin Backupbuddy it not MS compatible when I last checked,
A great source of premium WordPress multisite training, plugins and themes is WPMUDEV.org (aff)
A second compatibility consideration is your hosting. WordPress MS works in a different way to normal WP, please check with your hosting supplier to see if they support the requirements from http://codex.wordpress.org/Create_A_Network
More Difficult To Admin
Administration of WP MS is a little more difficult, there is the concept of a network administrator, who installs and enabled themes, plugins and site wide settings, next level down there is a site admin who can then admin only aspects of their own site.
This additional layer of administer has caused confusion in me, so be aware of this if you decide to go down this route.
Easier to manage multiple sites
This is the main benefit of MS, with one installation of WordPress, you can administer multiple WordPress sites.
Install a plugin once, and it is available to all sites it you network activate it.
Update WordPress once, and all of your sites are updated.
Sub Directories or Subdomains
When you install MS you get to control how your sites are configured. There are two options sub directories (the easiest method) or subdomains.
Subdirectories install your sites in the following fashion yourdomain.com/site1 yourdomain.com.site2
Sub domains create configurations like this site1.yourdomain.com site2.yourdomain.com.
There are also domain mapping plugins available for MS, which allow you to map a site to an alternative domain, for example you could setup yourdomain.com/site1 to map to the domain name mysecondcomain.com. This allows you to manage multiple domains from one install of WP. This is brilliant if you run multiple domains and want to reduce your admin overhead.
Are You Going Multisite
Are you going multisite? Just to recap you need more technical skills to manage a network, some of your plugins may not work, and lastly check out your hosting is compatible. Feel free to ask me any questions on multisite in the comments.