How to repair a corrupted Minecraft world

A world rarely corrupts without a reason. The usual causes are a crash mid-save, running out of disk space, a bad mod, or copying the world while the server was running. Most of the time the damage is small, such as a few broken chunks, and it can be fixed without losing the world. Here is how to tell what you have and how to repair it, starting with the least risky options.

First, do no harm

  1. Stop the server. Do not keep running a damaged world, because it can make things worse.
  2. Make a copy. Download the whole world folder, or duplicate it, before you touch it. Everything below should be done on the copy until you are sure.
  3. Check your backups. If you have a recent one, restoring is often the fastest fix. See Creating and restoring backups.

Signs of corruption

  • The server crashes whenever a player goes to a particular place, or at startup.
  • The console shows errors about a chunk or region that failed to load.
  • The world is missing, or the server generates a brand new one.
  • Players or items vanish, or land is reset to an older state.

The first error in the log tells you where to start. How to read your server logs explains how to find it.

Case 1: the whole world looks gone

If the server generates a fresh world, check three things before panicking:

  • The world name. In server.properties, level-name must match the folder name exactly. A typo or a changed name makes the server create a new world next to the old one.
  • The right folder. The old world may simply be sitting there unchanged.
  • level.dat. This file holds the world's core data. If it is damaged, the world will not load. The server keeps a backup called level.dat_old. Rename the broken level.dat to something else, then copy level.dat_old to level.dat and try again.

Case 2: a few chunks are broken

This is the most common case. The log names a region file or coordinates. World data lives in the region folder as .mca files, named r.X.Z.mca, and each file covers a square of 512 by 512 blocks.

To find which file holds a coordinate, divide the block coordinate by 512 and round down:

Block coordinateRegion number
0 to 5110
512 to 10231
-512 to -1-1
-1024 to -513-2

So a block at x = 1300, z = -200 is in region r.2.-1.mca.

You have two repair options:

Delete the broken region file. With the server stopped, remove the .mca file for that area, on your copy. The server regenerates the terrain when someone visits, and any builds in that region are lost. Only do this if the area is unimportant, or if the backup is not available.

Use a repair tool. The free MCA Selector program opens a world and lets you see and delete individual chunks, or chunks matching a condition. This is better than removing a whole region, because you only lose the damaged chunks.

Case 3: crashes caused by a mod or plugin

Sometimes the world itself is fine and an addition is the cause. If the problems began right after you added or updated something:

  1. Remove the newest mod or plugin.
  2. Start the server and see if the crash stops.
  3. If it does, the world may be undamaged. See My server crashes or won't start.

Case 4: disk full

A full disk is a leading cause of corruption, because the server cannot finish writing. Check your usage, as described in What the CPU, memory and disk numbers on your server mean, free up space, and then restore or repair.

After the repair

  1. Start the server and walk around the repaired area.
  2. Take a new backup straight away, so you have a good copy.
  3. Look for the cause: schedule backups, keep free space, and always stop the server cleanly with /stop.

Corruption is a reminder that a world without recent backups is at risk. Schedule automatic restarts and backups makes sure you always have one.

Still stuck? Open a ticket on Discord - run /ticket in any channel, pick a department, and include your Server ID or Invoice ID so we can jump straight in.