This is cool! For us toolmakers, any word on when this change is coming, and any deterministic way to tell the difference. Like, will something in level.dat specify the directory structure being used or should we just check if /regions exists then it's the old way, otherwise the new? Thank you. EDIT: On Twitter Dinnerbone said that "version" in level.dat will be increased. Currently Anvil worlds have a version of 19133, McRegion worlds before Anvil were 19132.