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Repair · Builder-world leftovers

NBT Doctor

Structures saved in a builder world carry that world's leftovers: vault timers, trial spawner cooldowns, fixed loot seeds, your name as an already rewarded player. NBT Doctor finds them and resets them to what Minecraft writes for a block that was never used. Everything runs in this browser.

  • Experimental
  • Minecraft Java
  • Runs locally
  1. 1Choose. A world folder, a zipped world, or a structure file.
  2. 2Check. Pick the rules. Every match is listed with its before and after.
  3. 3Download. A fixed copy, plus a JSON report of every change.

Check a world or structure

Drop your world folder here A Java world folder (the one with level.dat inside), a zipped world, or one structure file: .nbt, .schem, .litematic or .schematic. Bedrock is not supported.

Runs locally. Nothing is uploaded, this page has no processing server.

Fix these

Unticked rules are still found and listed, just not changed. Your choice is remembered in this browser.

Stuck the block will not work until it is reset. Leftover it works, but carries old data from the builder world.

FixRuleProblemWhat it does
Stuck An absolute game time of the world it was saved in. The vault stays inactive until this world's clock passes it.
Stuck Players who opened it in the builder world, usually you, can never open it here.
Leftover It was saved halfway through spitting out loot and resumes that in the new world.
Leftover Players who stood near it in the builder world. It draws particles to players who aren't there.
Stuck Absolute game times of the world it was saved in. The spawner stays in cooldown or waits to spawn until this world's clock passes them.
Leftover Players and mobs of a fight in the builder world, and loot it was about to drop.
Leftover Every copy of the structure rolls exactly the same loot. Without a seed each one rolls its own.
Leftover The success count drives comparators, so they show a result from the builder world.
Leftover Absolute coordinates of a flower in the builder world. Without them the bees look for flowers here.
Always reported, never changed (5)
  • End gateway: fixed exit The exit is a position in the builder world. Report only: without it the gateway makes a new exit, which only works in the End.
  • Jigsaw block left in the build Structure generation would replace it with its final state. A world editor places it as it is.
  • Structure block left in the build A build tool, placed as a working structure block.
  • Structure void left in the build An invisible build-tool block. Minecraft leaves it out of saved structures, so it came from elsewhere.
  • Container: items but no loot table Already opened in the builder world, or filled by hand on purpose. Report only.

Builder-world leftovers

Why a saved structure misbehaves

A structure saved from a world you built in keeps that world's block entity data: game-time timers that never pass in the new world, a loot seed that makes every copy roll identical items, and your own name as a player who already opened the vault. The blocks look fine and then simply do not work.

Each fix writes back what Minecraft itself writes for a block that was never used.

How it decidesRules, loot seeds, what is checked, limits

Each rule is a block entity id, a field and an action: set to zero, empty, or remove. Every fix writes what Minecraft writes for a block that was never used, so a clean block is left alone and fixing twice changes nothing the second time. Field names match Minecraft 26.3 and are the same back to 1.21.

Why loot seeds: a structure copied from a generated trial chamber keeps each chest's LootTableSeed, so every copy of it rolls the same items. Without the key, Minecraft rolls with the world's own random source when the container is first opened. The loot table itself stays. Untick the rule if identical loot is what you want.

What is checked: block entities in every dimension's region files (both the classic and the 26.x folder layout) and in structure files inside the world. Entities such as mobs or item frames are not checked. Unchanged chunks are copied byte for byte; changed chunks keep their compression. Chunks compressed with LZ4 are listed as not checked.

Limits: the complete world copy is capped at 3.9 GB (a browser zip limit); larger worlds get the changed files only. A zipped world is unpacked in memory, so very large worlds work better as a folder.