How the map is made
The world is generated in your browser by a port of Valheim's own world generator (the game's WorldGenerator, its biome sectors and ZoneSystem's location placement), with the location list of version 1.0.17 read from the game files: 200 kinds of location, from boss altars to shipwrecks. Each kind is placed the way the game does it, with the same random numbers, so the spots are the game's, not guesses.
Checked against a world Valheim generated on our PC (seed v6tBhYJErE): the biomes of all 4,194,304 cells of its minimap matched, its heights matched in 99.995% of them to the game's rounding, and all 12,372 of the 12,372 locations in its save came out at the same coordinates.
Ore, berries, mushrooms and trees (Layers → Resources) are placed zone by zone with the game's vegetation rules, including what already stands in the zone blocking a spot. In the 261 zones that world had generated, 95.9% of the 30,726 plants, rocks and deposits in its save came out within half a metre, and 99.3% in zones without a location; next to a location (its buildings, the ground it levels) a spot can differ. A world made in single player or by a hosting player and one made by a dedicated server differ here, because the game draws extra random numbers when there is a camera: pick yours in the panel.
Not decided by the seed: which of a trader's possible camps becomes the real one, and which way a building faces (the game rolls that when the area first loads). What each location holds is on its own page: see locations & dungeons, bosses and traders.
Looking for a good world?
We ran the generator over 1,000 random seeds and ranked them: bosses close to spawn, Haldor next door, the biggest land without a boat, every early biome on foot. In the middle world the nearest of Haldor's possible camps is 1.9 km from spawn; one world in ten has one within 1.5 km. Best Valheim seeds →
Questions
›Where do I find my world's seed?
In the game's world list, under the world's name (Start game → pick the world). Or drop the world's .fwl or .fwl2 file on the map: the seed is read in your browser, nothing is uploaded.
›Will the map match my world?
It runs the world generator of Valheim 1.0.17: terrain, biomes and where each location goes. Checked against a world the game made, all 12,372 saved locations came out at the same coordinates. Worlds made before the Mistlands update used an older generator, so their terrain differs.
›Why are there several spots for Haldor, Hildir and the Bog Witch?
The generator lays out several possible camps for each (Haldor 10, Hildir 10, Bog Witch 10). The first one a player comes near is where the camp appears, and the game removes the others. The same goes for the Forge of Potential.
›Does the map show silver, copper and berries?
Yes: in Layers → Resources. Ore shows on the whole map, plants and trees once you zoom in. They are placed with the game's vegetation rules; checked against a world the game made, 99.3% of spots away from locations matched. Choose whether your world was made in the game or by a dedicated server: trees and rocks come out slightly differently.
›How do I get to a location quickly?
Click a marker and copy its goto command. In the game, press F5, enter devcommands, then paste the command: it moves you to that spot.