The map itself is set. Some features, like the Trader have several possible locations and will appear at the first one you go to. You could play several games using the same seed and the map will always be the same.

OP am I right in guessing your custom preparing a world prior to play with Buddies? If so then the Upgrade_World by JereKuusela MOD is your friend here.

What i did was explore the world, Build some bases/quest areas.
run this mod to blank and re roll stuff like tar pits/caves etc
Hide the map again then uninstall the mod
The resultant db of the world has my prepared areas still but the fine details are still random so I still get some surprises when exploring .

That mod I feel ought to be in everyone's library (I access via thunderstore mod manager) as it allows excising worlds to get the new content without loosing builds without needing to run a fully modded server.

OFC if I'm wrong in my guess do tell! What have you got planned you have me intrigued!

If you just want to see what your seed looks like there is another way. https://valheim-map.world/
As far as have read about it and can recall, the world is created for 500m around you as you explore, so coming within that distance of a feature makes it populate. So yes you can reveal the map, but until you approach 500m of something it is not there.

BTW: not 100% sure it was 500m.

Good question: I believe that it will show you where they are but not generate them.

Reason I say that is by experimentation I have tried it and their is no significant increase in the games database file. Where as games with a lot of actually explored land have manifestly larger db files.

I just gets rid of the orange cloud obscuring the map for the whole world. It shows you the shape of all the islands and their biomes but no features (like the Trader). It is irrevocable - you can't undo it.

Originally posted by Zathabar:

Good question: I believe that it will show you where they are but not generate them.

Reason I say that is by experimentation I have tried it and their is no significant increase in the games database file. Where as games with a lot of actually explored land have manifestly larger db files.

Thank you! I was thinking of ways to test this but havent figured out a way how... Maybe ill just remake the world and not explore the map and restart the building. Only spent a few 4-5 hours so not the end of the world!

Originally posted by GrinfilledCelt:

I just gets rid of the orange cloud obscuring the map for the whole world. It shows you the shape of all the islands and their biomes but no features (like the Trader). It is irrevocable - you can't undo it.

I figured that, but the question is will the map be "generated" without me visiting the islands (like with an unexplored map)?