How to Fix Map Item Rendering Crash
A filled map whose data file is missing or damaged shows Unknown Map instead of crashing. Where map files live since 26.1 and how to fix a broken one.
Quick Fix
A map that shows Unknown Map has lost its data file. Restore data/minecraft/maps from a world backup, or clear the broken maps with /clear @s minecraft:filled_map and make new ones.
Error Message
Error loading saved data: SavedDataType[minecraft:maps/0]How to Fix
Close the world or stop the server before you change any map files.
Search the log for Error loading saved data to see which map ID is damaged.
Restore the damaged file, or the whole data/minecraft/maps folder, from a backup.
Without a backup, clear the broken maps with /clear @s minecraft:filled_map and craft new ones. A new map gets a new ID.
For a world from before 26.1, open it once in the new version and let the game move the map files instead of copying them yourself.
If there is a crash report, update or remove the map mod named in its stack trace.
Common Causes
- The map's data file is missing, for example after a world was copied without its data folder. Hovering over the map then shows Unknown Map.
- The data file is damaged. The log shows Error loading saved data with the map's ID, such as minecraft:maps/0.
- Map files were copied by hand between an old and a new world layout. Before 26.1 a map was saved as map_0.dat directly in the data folder, and since 26.1 it is 0.dat in data/minecraft/maps.
- A mod that draws maps crashed. That leaves a crash report, and its stack trace names the mod.
Diagnostic Steps
- Hover over the map and check for Unknown Map.
- Search the log for Error loading saved data.
- Restore the map file from a backup, or clear the map.
- Load the world again and check the map.
FAQ
Will I lose all my maps?
No. Every map has its own file named after its ID, so one damaged file only affects that map and its copies.
Where are map files stored?
In data/minecraft/maps inside the world folder since 26.1, as 0.dat, 1.dat and so on, next to last_id.dat with the last ID handed out. Older versions saved them as map_0.dat directly in the data folder.
What does Unknown Map mean?
The map item still has its ID, but the game can't find any saved data for that ID, so there is nothing to show on it.
