command to clean /fml/registry/... entries of deinstalled mods? in Suggestions Posted September 24, 2016 Only valid argument here would be lack of free IDs for new mods - which is ridiculous, I can't imagine any map having that much stuff. Ejem... Not a normal use case, but possible when you install a mod that it's really badly made (a single block id per block in a "huge library of blocks". Missing pieces for example. A frozen world, as another example. Do this mistake too many times and you are forced to abandon your map. Or manually fix it by removing block id by block id with nbtexplorer, which it works fairly well if you clean the map from those blocks with mcedit, which is a pita because you have to note down block ID by block ID what was added by the removed mod. A mod is removed? Fine. Put it's blocks/items/etc in a black list registry. Then an external tool can turn all that blacklisted blocks into id 0 and clean the blacklist entries after looking at all the chunks. Am I missing something here? As I see it, it's a registry entry and an external tool that loops it, not rocket science... items would be harded, I know, except that most of block containers are fairly standard (chests and such). Only mod blocks would be a problem, and not an uncontrollable problem. And the point of letting players keep using a map that they played in for months? Well... do I really have to explain that?