This article may be outdated and contain information pertaining to an older version of WordPress. Please take caution when following the procedure, as many things may have changed.

Note: Site wide tagging is introduced in WPMU version 1.3, so this approach might be considered obsolete.

This solution for creating sitewide categories in WordPressMU uses a separate standard single-user WordPress install to read the sitewide feed WordPress Plugin from within WordPressMU. Using a Sitewide Categories WordPress Plugin, it creates tags. This is based on the WordPressMU Support Forum discussion on sitewide categories.

You will need:

1. Completed WordPressMU installation
2. The WPMU Sitewide Feed Plugin or similar
3. The Tag Replaces Post Link WordPress Plugin
4. WP Autoblog WordPress Plugin
5. A single user blog activated on the WordPressMU installation. It can be called "tags.example.com" or "categories.example.com" or something else

The step-by-step process is as follows:

1. In the Single User WordPress blog, set the following:
   1. On Admin > Options > General
      1. Uncheck 'Anyone can register' is unchecked
   2. On Admin > Options > Reading:
      1. Change the Syndication Feeds to Summary (Optional but suggested)
      2. Bump up the Show the Most Recent to something like 25. (Optional)
   3. On Admin > Options > Privacy
      1. Change Blog Visibility to 'I would like to block search engines, but allow normal visitors. This setp is VERY IMPORTANT! Turn off Pings for the blog to avoid tracking and multiple pings.
   4. On Admin > Options > Discussion. This is VERY IMPORTANT to turn off the first three options under 'Usual settings for an article':
      1. Turn off "Attempt to notify any Weblogs linked to from the article (slows down posting.)"
      2. Turn off "Allow link notifications from other Weblogs (pingbacks and trackbacks.)"
      3. Turn off "Allow people to post comments on the article"
      4. Turn on "Before a comment appears: An administrator must always approve the comment" (this blog is not to host comments)
   5. On Admin > Options > Permalinks
      1. Change Permalinks to 'Date and name based'
2. On the Single User WordPress
   1. Download and enable the Tag Replaces Post Link WordPress Plugin:
3. On the Administration Panels of WordPressMU go to SiteAdmin > Sitefeed
   1. Change Trigger Blog ID to a high number that it does not refer to an active blog, such as 1000 (You will change it back after the first import.)
4. Insall and activate the WP Autoblog WordPress Plugin.
5. On your single WordPressMU blog's tag system installation, go Dashboard > Options > WP Autoblog
   1. Enter the URL of your WPMUFeed into the basic settings box on the left. Optionally, choose the Excerpt and credit options.
6. Double check the pings are in fact turned off on the single user blog blog.
7. On the Single User WordPress, Options > WP AutoBlog > Run Script Now. It should import all the posts from the sitewide blogs on the WordPressMU installation into the single user blog.
8. On WordPressMU Administration Panels > SiteAdmin > Sitefeed, change the Trigger Blog Id back to the normal number.

These changes with the Tag Replace Post Link WordPress Plugin or similar to allow the "tag system" to load the URL of the individual blog as the permalink instead of the normal URL of the blog's post.