Tutorial:Repairing a world corrupted by a data pack

This tutorial is a guide for repairing worlds that are no longer loadable (even in safe mode) due to a previously enabled datapack being disabled, missing, or outdated.

Missing biomes in a vanilla dimension

A vanilla dimension generated a datapack-created biome, which is now invalid or no longer present.

• Navigate to the world's level.dat file and open it in a .dat file editor such as WebNBT or NBTExplorer.
• Navigate in the file to "Data" → "WorldGenSettings" → "Dimensions" → (The dimension where this biome previously generated) → "biome_source"
• Remove the list tag "biomes" if it exists.
• Create a string tag with the name "preset" and set its value to the dimension's id. (eg: minecraft:overworld)
• Save the file and load the game.

All missing biomes will become the plains biome.

Missing dimension in a Minecraft server

The Minecraft server will not load because a previously generated custom dimension is now invalid or no longer present. Note that this only causes an error on a Minecraft server, not singleplayer.

• Navigate to the server's level.dat file and open it in a .dat file editor such as WebNBT or NBTExplorer.
• Navigate in the file to "Data" → "WorldGenSettings" → "Dimensions"
• Remove the compound tag for the invalid/missing dimension.
• Check if your server has other level.dat files in other folders. If it does, repeat the first 3 steps for each one.
• Save the file(s) and start the server.

Everything inside the custom dimension will be saved, but can no longer be loaded. Any players that were inside it when it was removed will now be in the overworld.