Minecraft wiki entry for Creating_behavior_packs, associated text: The behavior pack is now game ready. to test it, open minecraft, go to a world on which you want to test it. go to the world settings, navigate to the addons menu, and find it under my packs. it will now work on your worlds. this is where the "version" line in the manifest.json file becomes important. anytime you modify anything in the development pack, the world will continue to run the old version unless the pack version is higher.