World Doctor

World won't load? Drop it in and we'll fix it.

Drop your world here

Java: the world folder or a .zip of it. Bedrock: the .mcworld file. It never leaves this device.

folder.zip.mcworld

What it checks

Every chunk, the way Minecraft reads it
The world's settings (level.dat) and each player
Pieces saved in the wrong place, or on top of each other
Item piles that freeze the game, and version mix-ups

You always get a fixed copy. Your original stays exactly as it is.

What it does

Checks every chunk the way Minecraft reads it: pointers, lengths, compression (gzip, zlib, none, LZ4) and the data inside

Takes out broken chunks cleanly so Minecraft grows them again, instead of erroring or crashing

Moves chunks saved in the wrong place back to where they belong

Restores level.dat and player files from Minecraft's own backups

Clears huge piles of dropped items that freeze the game

Warns when a world was made in a newer Minecraft than yours

Bedrock: repairs level.dat and the database's index, and finds missing or damaged map files

Bring my inventory back: after moving a world between singleplayer and a server or Realm, puts your inventory, ender chest, XP and position where the game looks (Java; Bedrock in testing)

Makes a fixed copy with a list of exactly what changed; runs in your browser

Questions

Will fixing my world delete my builds?

Only chunks Minecraft already can't read are taken out — the game throws those away itself when it tries to load them, so nothing you could still see is lost. Taking them out cleanly just stops the errors and crashes, and Minecraft grows fresh land in those spots. Everything else is copied byte for byte into a new copy; your original isn't changed.

What is a “chunk in the wrong location”?

Every chunk records its own position. If a tool or a crash files it in the wrong slot, Minecraft logs “Chunk file is in the wrong location” and the land shows up in the wrong place. World Doctor moves it back where it belongs, or removes it if it's just a stray copy of a chunk that's already there.

My world says it was made in a newer version. Can you fix that?

No — and nothing can safely. Newer versions save blocks and items older ones don't know. Open the world in that newer version (or newer) instead.

Does it work for Bedrock worlds?

Partly, for now. It checks and repairs level.dat (from the backup, or a wrong header), rebuilds the database's CURRENT file, and tells you exactly which map files are missing or damaged. Repairing the chunks inside the database is coming soon.

I moved my world to a server (or back to singleplayer) and my inventory is empty. Can I get it back?

Usually, yes — it's still in the world, just saved where the game no longer looks. Singleplayer and servers keep players in different places (Java: level.dat or singleplayer_uuid versus each account's player file; Bedrock: ~local_player versus player_server_ records), and offline-mode servers name players differently from real accounts. Drop the world in, pick “This is me” on the player with your stuff, choose singleplayer or a server or Realm, and download the fixed copy. For a server, type the name you join with — normal or offline server. Java works now; Bedrock is still being tested.

Is my world uploaded anywhere?

No. Everything happens in your browser on your own device, and the fixed copy is made there too.