Originally posted by electricdawn:

No, backups are not done automatically. How would the computer know where to put them? Apple‘s macOS does a pretty good job of doing backups for you, but even there you need to activate it first and give it a place where to store stuff second. Backups in Windows just plain sucks, you better use a third party solution.

Actually they are. If you go into your Valheim world files there will be a file with the extension .old. That is your backup file.