Can’t Change Category Slug

WordPress LogoI just spent about 20 mins trying to figure out why WordPress wouldn’t let me change one of my category slugs. It kept appending “-2” onto the end of it, obviously because the slug was in use elsewhere.

It turns out that WordPress combines Links categories and Posts categories and they all have to be unique. So if you already have a Links category slug with the name of the Posts category slug you want to use, you can’t.