Valheim mods with BepInEx: server and client

Modding Valheim runs through BepInEx, and almost every problem on a modded server comes from the same misunderstanding: not every mod goes in the same place, and not every mod has to be installed by everyone.

Three kinds of mod

• Server-side only. They change world rules — spawn rates, damage, day length. Players need nothing. These are the easiest to live with.
• Client-side only. They change what one player sees: interface, minimap, quality-of-life. The server neither knows nor cares.
• Both sides. They add content — items, structures, creatures. Everyone must run the same mod at the same version, server included.

That third category causes the failures. A client with a missing or mismatched mod does not get a clear error: it gets a refused connection or an object it cannot render.

Version alignment is the whole job

A content mod updated on one side and not the other is the same as a missing mod. The practical consequences:

• Freeze your mod list. Write down every mod and its exact version, and treat that list as the source of truth for the server and for the players.
• Never update a single mod alone. Update the server and announce the list to your players in the same operation.
• Expect breakage after a game patch. A Valheim update usually requires BepInEx and the mods to follow, and the gap between the two is when servers go down.

Where files go on the server

BepInEx installs alongside the server, and mods go in its plugins folder. Two points that trip people up:

• The start script must be the one BepInEx provides, not the vanilla one. Launching the vanilla script starts a perfectly working server with zero mods loaded — and no error.
• Configuration files are generated on first launch, not at install. You have to start once before you can tune anything.

Whether to run mods at all

Mods cost more than the install. They cost a mod list to maintain, players to keep aligned, and downtime after every game patch. Worth it for content mods that genuinely change the game; much less so for three quality-of-life tweaks that each player could install client-side on their own.

A reasonable rule: server-side and client-side mods, freely. Content mods, deliberately.

Whatever you run, you need full file access to install BepInEx and manage the plugins folder. Our Valheim server hosting gives full WebFTP access for exactly that.