Custom Taxonomy Cleanup
A WordPress plugin to detect and delete terms from custom taxonomies that are no longer in use
Install
This is the repository archive. It installs, but the folder name will carry the branch suffix and updates will not flow.
Install straight from GitHub with WP-CLI:
wp plugin install https://github.com/keesiemeijer/custom-taxonomy-cleanup/archive/refs/heads/master.zipCustom Taxonomy Cleanup 
Custom taxonomy terms are left in the database if a taxonomy is no longer registered (in use).
Plugins and themes can (without you knowing) use custom taxomies as a way to store data. These terms stay in the database forever if they're not cleaned up by the plugin/theme itself upon deletion.
This plugin provides an easy way to detect and remove terms from taxonomies that are no longer in use. The settings page for this plugin is at wp-admin > Tools > Custom Taxonomy Cleanup.
Note: The proper WordPress delete function wp_delete_term() is used instead of running a direct MySQL query to delete the terms.
It's recommended you make a database backup before deleting terms.
Check out this sister plugin to delete unused custom post type posts.
Screenshots
No terms found
The settings page if there are no terms from unused taxonomies in the database. De-activate or delete the plugin and use it again later.
Settings Page
The settings page if terms where found (after deleting a batch of 100 terms).
Done
The settings page if all terms were deleted. De-activate or delete the plugin and use it again later.
