Last modified: 2012-07-18 16:49:27 UTC
Originally reported by an IRC user. Now api.php?action=query&list=allcategories returns all rows in category table, while [[Special:Categories]] filters out empty categroies, which is confusing.
Bug 38279
related: bug 26411
With Gerrit change #15604 the same condition was added to list=allpages, which is already used on Special:Categories (cat_pages > 0). Maybe that is enough to fix this bug.
You can use acmin=1 to exclude empty categories from list=allpages