Valheim Server Settings and Launch Arguments

Valheim has no server config file. Everything is set with launch arguments, which on your hosted Valheim server means the fields in the Startup tab. This guide covers every argument Iron Gate documents, the world modifier system and its ordering rule, the three permission files, and world management.

How Valheim server settings work

There is no server.cfg to edit. The server reads its entire configuration from the command line at startup, so every setting is either a Startup field or an extra launch argument.

The password is the most common connection failure

On a public server — and public is the default — Valheim refuses a password shorter than 5 characters, and also refuses one that appears inside the world name or seed. It does not start with a bad password: it logs Error bad password: and exits. If the server dies on boot, or players report failures immediately after you change settings, check this first — it is the fault most often mistaken for a version mismatch after an update.

-port is the panel's, and Valheim uses two ports

Valheim binds your chosen port and the next one up — the stock 2456 means 2456 and 2457. Your allocation is on the Network tab and the panel sets it for you. Adding your own -port argument almost always breaks connectivity, because the second port will not be open.

Crossplay: the argument that decides who can join

-crossplay is a single flag with an unusually large consequence, and it is off unless you add it. Iron Gate's dedicated server guide puts it plainly:

"-crossplay - Runs the Server on the Crossplay backend (PlayFab), which lets users from any platform join.
If you do not include this argument, the Steam backend is used, which means only Steam users can see and join the Server."

Until now that mattered to Xbox players. From 9 September 2026 it decides a great deal more. Iron Gate's release announcement, dated 7 June 2026, confirms 1.0 lands on "PC, Linux, Mac, Xbox One and Xbox Series X|S as per usual, and now we’re also adding PlayStation 5 and Nintendo Switch 2 to the roster", with "full crossplay between all the platforms". A server left on the default Steam backend is invisible to every one of those console players, and there is no way for them to work around it from their end.

Set this before you sell anyone on joining

-crossplay is a launch argument, so it is read once at boot and changing it means a restart. If any of your players are on Xbox, PlayStation or Switch, put it in the Startup tab now and test a join while nobody is waiting on you — not on launch day. Valheim 1.0: What Changes for Server Owners has the rest of the pre-launch list.

Two knock-on effects are worth knowing about.

Crossplay servers hand out a join code. Iron Gate's Crossplay FAQ describes the flow:

"When you start a server through the game or by hosting a dedicated server, you’ll be able to see a “Join code” by entering the pause menu. Copy the code by simply clicking on it and send it to your friend! Your friend will then have to head over to the “Join Game” section, press “Add server” and paste the code."

Port forwarding stops mattering. From the dedicated server guide:

"If you’re using the Crossplay backend (enabled using the “-crossplay” argument), you do not need to do Port Forwarding on your Router. The Port number is still used to distinguish between multiple servers on the same public IP address."

On a hosted server the panel opens your ports either way, so that only changes things if you also run a server at home.

One thing -crossplay cannot fix from the server side is the player's own account settings. The Crossplay FAQ notes that an Xbox player who "can't find the option to enable crossplay" may need to adjust their parental control settings — a client-side toggle, not a server one.

Is Valheim Crossplay? PC, Xbox, PS5 & Switch 2 Explained covers what each platform can and cannot do, and how players on each one actually connect.

Save and backup arguments

These are rarely set and genuinely useful, because Valheim's own backup behaviour is separate from your panel's Backups tab:

Lowering -saveinterval reduces how much progress a crash can cost, at the price of a brief stutter on each save. On a busy server 900 (15 minutes) is a reasonable compromise.

Valheim's backups are not a substitute for the panel's

-backups keeps copies inside the same server. If the underlying save is corrupted or deleted, those copies usually go with it. Use the Backups tab for real snapshots — see How to Create a Backup.

World modifiers

Valheim ships official difficulty modifiers. On a dedicated server they are applied as launch arguments, which enforces them for everyone rather than letting each player choose.

There are three argument types:

-preset applies a whole tuned profile at once:

-preset casual

Available presets: normal, casual, easy, hard, hardcore, immersive, hammer.

-modifier sets one dial:

-modifier resources muchmore -modifier raids none

-setkey toggles a switch on:

-setkey nobuildcost -setkey passivemobs

Available keys: nobuildcost, playerevents, passivemobs, nomap.

Order matters — put -preset first

The server reads arguments in sequence, and later ones overwrite earlier ones. A -preset placed after your -modifier arguments will flatten every one of them back to the preset's values.

Always write -preset first, then -modifier, then -setkey:

-preset casual -modifier resources most -setkey nobuildcost

Reversed, the -preset casual at the end would silently discard the resource change.

Modifiers attach to the world they launch with

They apply to the world loaded by that startup, so a modifier set for one world does not follow you when you switch -world to another.

Admins, bans and whitelists

Three plain-text files control access. They live in the save directory, alongside worlds_local/, and each takes one ID per line.

Iron Gate documents the format as one Platform User ID per line, written [Platform]_[UserID] and case-sensitive:

Steam_76561197960287930

Two formats are in circulation — copy the one the game shows you

Iron Gate's dedicated server guide asks for that prefixed Platform User ID and says it "can be obtained from the Server log or from within the game using the F2 panel". Almost every third-party guide instead shows a bare 17-digit SteamID64 with no prefix, which is the format that predates crossplay, and that form is still widely reported to work. Nothing authoritative settles which the parser prefers, so do not guess between them: press F2 in game, or read the line the server console prints as the player joins, and paste the ID exactly as it appears. If admin rights refuse to apply, re-check this first.

Crossplay makes the prefix matter more, because a player arriving from Xbox or the crossplay backend has no SteamID64 to fall back on. Whatever the F2 panel prints for them is what belongs in the file. Restart the server after editing any of the three files.

permittedlist.txt is all-or-nothing

The moment it contains a single entry, everyone not listed is refused. If you add yourself to test it and then cannot work out why your players vanished, that is why. Leave it empty unless you want a closed server.

In-game, admins press F5 for the console, which has to be enabled first — either from the Gameplay settings menu, a toggle Iron Gate added in patch 0.221.4, or with the older -console launch argument. Note that item spawning and teleporting rely on developer commands, which dedicated servers restrict by default. See Valheim Console Commands for the full list, both ways of switching the console on, and which commands a dedicated server will accept.

World management

Worlds live in worlds_local/, two files each:

• MyWorld.db — the world data
• MyWorld.fwl — the metadata

Switching worlds: change the World Name in the Startup tab. Valheim loads the world if it exists and generates a new one if it does not.

Uploading a single-player world: there is a longer guide to moving an existing world onto your server, covering the Steam Cloud and macOS cases. In short:

1. On Windows, find it at %USERPROFILE%\AppData\LocalLow\IronGate\Valheim\worlds_local\.
2. Upload both the .db and .fwl to worlds_local/ — see How to Upload Files via SFTP.
3. Set World Name to match, without the extension.
4. Restart.

A wipe means deleting both files

Stop the server, delete the .db and the .fwl, then start. Deleting only one leaves the world in a broken state rather than regenerating it cleanly.

Applying changes

Startup fields and launch arguments are read once, at boot. Save your changes and restart — there is no way to apply them to a running server.

What to read next

• Getting started with your Valheim server — first boot and connecting
• Valheim Console Commands — the F5 console and what dedicated servers allow
• How to install mods for your Valheim server — BepInEx and Thunderstore
• Maintaining your Valheim server — restarts, backups and troubleshooting

FAQ

Where is the Valheim server config file?

There isn't one. Valheim is configured entirely through launch arguments, which on a hosted server are the fields and extra arguments in the Startup tab.

Why can nobody join my Valheim server?

Most often the password. On a public server Valheim rejects anything under 5 characters, and anything that appears inside the world name or seed — it exits on boot with Error bad password: rather than running. After that, check that Public is set as you intend and that you have not overridden the panel's port.

How do I make someone an admin?

Add their ID to adminlist.txt, one per line, and restart. Iron Gate documents the format as a case-sensitive [Platform]_[UserID], for example Steam_76561197960287930, while bare SteamID64s are widely reported to work as well. Press F2 in game and copy the ID exactly as it appears rather than choosing between the two.

Why did my world modifiers stop working?

Almost always argument order. A -preset after your -modifier arguments resets them. Put -preset first.

How many ports does Valheim need?

Two — the one you are given and the next one up. The panel handles this, which is why you should not set -port yourself.

Do I need -crossplay for PlayStation, Switch or Xbox players?

Yes. Iron Gate's dedicated server guide is explicit that without the -crossplay argument the server runs on the Steam backend, "which means only Steam users can see and join the Server". Valheim 1.0 adds PlayStation 5 and Nintendo Switch 2 alongside the existing Xbox versions on 9 September 2026, so from that date a default-configured server is invisible to three console audiences. Add the argument and restart. Is Valheim Crossplay? has the platform detail.

How do I whitelist my server?

Add IDs to permittedlist.txt. Be aware that a single entry immediately locks out everyone not on the list.

Do settings changes need a restart?

Yes. Launch arguments are read only at startup.

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