World Incompatibility Errors When Changing Server Version

When switching your server to a different Minecraft version, you may encounter one of the following errors:

Error 1 — Upgrading to a newer version:

WARN: java.lang.RuntimeException: Server attempted to load chunk saved with newer version of minecraft! 4903 > 4790

Error 2 — Downgrading to an older version:

java.lang.IllegalStateException: No key dimensions in MapLike[{}]; No key seed in MapLike[{}]

Why this happens

Both errors occur because your existing world files are incompatible with the new server version. Minecraft stores world and chunk data tied to the version it was created on, and switching versions — whether upgrading or downgrading — can cause the server to fail to read it correctly.

How to fix it

⚠️ Warning: This will delete your current world. Back it up first if you want to keep it.

1. Stop your server.
2. Go to the Files tab in your panel.
3. Delete the world folder(s):
   • world
   • world_nether
   • world_the_end
4. Restart your server. A fresh world compatible with the new version will be generated automatically.

📝 Note: Always back up your world before switching server versions to avoid losing your progress.