Valheim 0.221.13

Patch 0.221.13 is a public test build, so it may be unstable, and it replaces how Valheim stores your worlds. Instead of one big file, worlds are now saved in smaller pieces, and only the pieces that changed get rewritten. The aim is quicker saving and a lower chance of corrupt saves, and the developers say most players will only notice the faster saves.

New content 4

A new world save system saves worlds in smaller chunks, and only chunks modified since the last save are written.
Worlds are no longer stored as a .db file and a .fwl file; each world now lives in its own folder, with the .db data split into multiple chunk files.
Backups are now kept in their own separate folders.
After saving, the game runs extra checks to confirm the save worked properly, which lowers the risk of corrupt saves.

Changes and balancing 3

Only world saves use the new system; character saves stay the same.
When you load a world that is not yet chunked, the game first makes a backup so no data is lost if new bugs appear.
Cloud storage now has an extra limit: until now only the total size of all saves counted, but some platforms cap the number of files, and worlds will now produce many more files.

Known issues 2

If you plan to switch between the Public Test branch and the Live branch, moving your save files around manually is not advised.
The new save system has not been tested with mods, and modding is done at your own risk.