Board Thread:Support Requests - Getting Technical/@comment-1827503-20141115102625/@comment-5558012-20141115150926

Just deleting category pages will leave category red links in a page's category section. To uncategorize everything I would use AWB to remove categories from the pages and then delete the categories (there is likely an easier way to do this as AWB will remove all pages from a single category in separate edits instead of all categories from a page). Given the number of categories you will be changing, a bot flag will definitely be needed. Dev has a couple scripts (Rename and MassCategorization) that can be used (strongly recommended with a bot flag as well) instead of deleting everything or used to re-categorize.