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Corrupted world, region, or config file
COAL-016 · Corrupted file
The server reported something on disk as corrupted. How to tell which file, when to restore a backup, and how to stop it happening again.
What it looks like in the log[Server thread/ERROR]: Region file .../region/r.0.0.mca is corrupted [Server thread/ERROR]: Failed to load chunk 12, -3
What it means
A file did not contain what the server expected - truncated, half-written, or invalid. The overwhelming cause is an unclean shutdown: killing the process, closing the window, or losing power mid-save leaves a region file written halfway. Disk problems and running out of free space account for most of the rest.
How to fix it
- Identify the file from the message. A
.mcafile is world data,level.datis world metadata, and anything in a mod's config folder is usually safe to delete and let regenerate. - For
level.dat, Minecraft keepslevel.dat_oldright beside it. Renaming that over the broken one recovers most cases without touching your world. - For a region file, restore just that file from a backup, or delete it and let the chunk regenerate - you lose the builds in that region, not the world.
- For a mod cache or config, delete the folder (not the jar) and let the mod rebuild it.
- Then fix the cause. Always stop the server with the
stopcommand rather than by closing the window, and keep automated backups running so the next occurrence costs you minutes instead of the world.