Valheim: Set Dedicated-Server Difficulty and World Modifiers

On a Valheim dedicated server, you set a difficulty preset and individual world modifiers in the startup file. The official Steam server guide documents -preset, -modifier, and -setkey for this configuration.

Argument order matters when you combine a preset with exceptions: a preset overwrites modifiers placed before it. Put the preset first and the exceptions afterward. You can keep your existing world name and password while changing these settings.

Prepare the Startup File

Stop a running server with Ctrl+C in its command window. To find the installation folder, right-click Valheim Dedicated Server in your Steam Library and choose Manage → Browse Local Files. If the server program is not installed, enable Tools in the Library and install it.

Copy start_headless_server.bat on Windows or start_server.sh on Linux, then edit the copy. Steam updates reset the original file. Add the arguments to the existing server launch command, keeping -world and -password unchanged if you only want to adjust difficulty. Save the file and launch your edited copy directly; the Steam shortcut launches the original filename.

Put the Preset Before Its Exceptions

The documented -preset values are Normal, Casual, Easy, Hard, Hardcore, Immersive, and Hammer. Place individual -modifier settings after the preset. For example, -preset hard -modifier raids none puts the raid exception after the Hard preset, following the documented order.

The documented modifiers and values are:

Combat: veryeasy, easy, hard, veryhard
DeathPenalty: casual, veryeasy, easy, hard, hardcore
Resources: muchless, less, more, muchmore, most
Raids: none, muchless, less, more, muchmore
Portals: casual, hard, veryhard

You can also use -setkey with one of the documented keys: nobuildcost, playerevents, passivemobs, or nomap.

If Your Change Does Not Apply

Check that you launched the edited copy, that -preset precedes your -modifier exceptions, and that -world still names the intended world. Game server connected means the server is ready to accept connections; the message does not establish the effect of a particular modifier.