What are WordPress orphaned user meta and how to clean them?

The user metadata is the information you provide to viewers about each user. This information usually includes additional data that is not stored in the users’ table of WordPress. In some cases, some user metadata information become orphaned and does not belong to any user. They are then called “orphaned user meta” and should be cleaned since they are not useful.

To clean this orphaned user meta, you can either use our plugin Advanced Database Cleaner, or execute the following SQL code (which is used by the plugin) directly via your phpMyAdmin:

DELETE FROM usermeta WHERE user_id NOT IN (SELECT ID FROM users)