Minecraft wiki entry for Region_file_format, associated text: Beta 1.3 converts any "old" chunks into region files before loading the world, rather than incrementally as they are loaded during play. As part of the conversion, level.dat is updated with TAG_Int("version") (note case) set to 19132. Beta 1.3 also introduces a new level name field, TAG_String("LevelName"). There's also introduced new TAG_Byte("Sleeping") in player TAG_Compounds - level.dat in singleplayer, [player name].dat in multiplayer that indicates whether is player in the bed. It has value 1(true) or 0(false). For the beta 1.8, TAG_Int("GameType") was added. In beta 1.9, TAG_byte("hardcore") was added.