Valheim server launch parameters, one by one

A Valheim server is configured almost entirely through its launch line. There is no large config file to edit: everything lives in a handful of parameters, and two of them will stop the server from booting if you get them wrong.

The four required parameters

-name

The name shown in the server list. It has no technical effect, but it carries one rule: the password must not appear in it, even partially. The server refuses to start if it does.

-port

The listening port, UDP. Valheim actually uses two consecutive ports: the one you set, and the next one. Opening only the first gives you a server that boots and stays invisible.

-world

The world name. If it does not exist it is created; if it does, it is loaded. This name also determines the save file names, so changing it starts a fresh world rather than renaming the existing one.

-password

Five characters minimum. That is the second condition for a successful boot, alongside the naming rule above.

The parameters that change behaviour

-public

Set to 1, the server advertises itself in the community list. Set to 0 it stays reachable, but only by direct connection. Switching to 0 is the simplest way to cut unwanted join attempts without touching anything else.

-crossplay

Routes the server through the platform network instead of Steam alone, which is what lets players on other platforms join. The trade-off: direct IP connection no longer works the same way, and some Steam players find the server less easily.

-savedir

Moves the worlds and characters folder. Rarely needed in single player, essential as soon as you want saves living somewhere other than the user profile — on a separately backed-up volume, for instance.

The mistakes that come up most

• Password inside the server name. The error message is explicit, but it scrolls past in the console before most people read it.
• Only one port opened. The server runs, the logs look clean, and nobody can connect.
• Renaming the world. Changing -world renames nothing: it creates a new empty world and leaves the old one on disk.
• TCP instead of UDP. Valheim only listens on UDP; a TCP forward does nothing.

Checking the config actually applied

The server log states the world it loaded and the port it really listens on at boot. That is the only reliable place: if what you read there does not match your launch line, the start script being used is not the one you think.

On a rented instance these are exposed in a panel rather than a script. Our Valheim hosting shows them in plain form, which removes that whole class of mistakes while keeping file access for anyone who prefers editing directly.