Starting with Valheim mods, and the two that change everything

Valheim's modding scene is smaller than the giants and noticeably better behaved. Most of it runs through one loader, most of it is on one platform, and the conventions are consistent enough that mods generally cooperate.

Back up the world first

Not advice, a prerequisite.

Valheim writes your world and your character as files, and a world touched by a mod that added objects contains references to those objects. Remove the mod and the game finds references it cannot resolve, and drops what it cannot load. That includes the base you built out of it.

Copy the worlds and characters folders somewhere the game cannot reach before you install anything. Adding mods rarely goes wrong. Removing them is where the damage happens, and by then it is too late to take a copy.

The loader

BepInEx, next to the game executable, launched once before anything else. Same as every other Unity game with a scene. If you have modded Lethal Company or Risk of Rain 2, this is the same procedure.

Where to start

Two categories are worth installing before anything ambitious, because they change how the rest of the experience feels.

Quality of life mods that adjust the parts of the game that are slow rather than hard: inventory handling, build placement, map behaviour. These have no effect on anyone else and are the safest thing to add.

Configuration mods that expose the game's own numbers, so you can adjust difficulty and rates without installing anything that adds content. Often the answer to a complaint that would otherwise take five separate mods.

Content mods that add biomes, creatures or systems come after, once you have a setup that starts reliably and a copy of your world.

Dedicated servers

If you play on a dedicated server, the server needs the same mods your clients do, at the same versions, for anything that touches gameplay. That is not optional and the failure is not graceful.

Update the server first, then the clients. A client ahead of a server is a connection that fails immediately, which is easier to diagnose than the other way around.

When the game updates

Valheim's patches have historically been large, which means most mods break together and most get fixed together. The loader usually needs updating too.

Nothing here is urgent. A world on the previous version keeps working on the previous version, and staying there for a fortnight while the scene catches up costs nothing except the patch notes.