Valheim Server Configuration Guide

Valheim Server Settings: Launch Arguments, World Modifiers, Save Location and Ports

A Valheim dedicated server has no settings file. Everything is set by arguments on its start line, plus three small text files that decide who is an admin, who is banned and who may join. This guide goes through every argument in Iron Gate's server manual, what each world modifier and preset really changes, where the world is saved and how to move one in, and which ports matter with and without crossplay.

Which version this covers. Valheim left Early Access with version 1.0 on 9 September 2026, and 1.0 changed how worlds are saved. Everything here was checked on dedicated server 1.0.16 installed with SteamCMD (app 896660) on Linux, against the Valheim Dedicated Server Manual PDF that ships with the server and Iron Gate's patch notes. Where we write "in our test", we started that server and looked at what it did.

The Start Line

On Windows the server is started by start_headless_server.bat, and on Linux by start_server.sh, both in the server's install folder. The Linux script that ships with 1.0.16 starts the server with this line:

Steam resets both scripts every time the server updates, so the manual tells you to make a copy, edit the copy and start the server from it. Note that the shipped script already includes -crossplay; if you want a Steam-only server, remove it (see ports below).

Every Launch Argument

Argument	Default	What it does
-name "My server"	–	The name shown in the server list.
-port 2456	2456	The game port. The server uses this port and the next one (2456 and 2457 by default). On a crossplay server the number is still used to tell apart servers that share a public IP.
-world "Dedicated"	–	The world to load. If no world with that name exists, a new one is created with a random seed.
-password "secret"	–	The password players must enter. Iron Gate's start script states the rules: at least 5 characters, and the password can't be contained in the server name.
-public 1	1	1 lists the server in the in-game browser. 0 hides it; players then join with Join IP. The manual suggests 0 for a LAN server.
-savedir [path]	see below	Where worlds and the admin, ban and permitted lists are stored.
-logFile "path"	–	Writes the server log to this file.
-saveinterval 1800	1800	Seconds between world saves (30 minutes).
-backups 4	4	How many automatic backups to keep. The first is taken at the short interval, the rest at the long one: by default one backup 2 hours old and three 12 hours apart.
-backupshort 7200	7200	Seconds before the first automatic backup (2 hours).
-backuplong 43200	43200	Seconds between the later automatic backups (12 hours).
-crossplay	off	Runs the server on the crossplay backend (PlayFab), so players on every platform can join. Without it the Steam backend is used and only Steam players can see and join the server.
-instanceid "1"	–	Only for several servers on the same port from the same machine (same MAC address): give each a different value so each gets its own PlayFab ID.
-preset hard	–	Applies a world modifier preset. Valid values: Normal, Casual, Easy, Hard, Hardcore, Immersive, Hammer.
-modifier raids none	–	Sets one world modifier. Repeat it for each modifier you want to change.
-setkey nomap	–	Turns on one world modifier checkbox. Repeat it for each one.

The values in the Default column are the ones the manual gives. The community wiki's example start lines also add -nographics -batchmode.

World Modifiers: Presets, Modifiers and Checkboxes

These three arguments set the same options as the World Modifiers screen in the game. A modifier is stored in the world as a "global key", and a key at 100 means normal. To see exactly what each value does, we started a 1.0.16 server with each value and read the keys it saved into the world.

-modifier: the five sliders

Modifier	Values	What the server stored
combat	veryeasy, easy, hard, veryhard	veryeasy: player damage 125, enemy damage 50, enemy speed and size 90 easy: player damage 110, enemy damage 75, enemy speed and size 95 hard: player damage 85, enemy damage 150, enemy speed and size 110, enemy level-up rate 120 veryhard: player damage 70, enemy damage 200, enemy speed and size 120, enemy level-up rate 140
deathpenalty	casual, veryeasy, easy, hard, hardcore	casual: equipped items are kept, skill loss rate 15 veryeasy: skill loss rate 15 easy: skill loss rate 50 hard: unequipped items are deleted, skill loss rate 150 hardcore: all items are deleted and all skills reset
resources	muchless, less, more, muchmore, most	Resource rate 50, 75, 150, 200 and 300 (0.5x to 3x).
raids	none, muchless, less, more, muchmore	Event rate 0, 200, 150, 60 and 30. A higher event rate means more time between raids; 0 turns raids off.
portals	casual, hard, veryhard	casual: every item can go through portals, ores and metals included hard: portals can't be used near an active boss veryhard: no portals at all

The manual lists no "normal" value for a single modifier: normal is simply the absence of the key. To put everything back to normal, use -preset normal (below).

-setkey: the checkboxes

Key	Effect
nobuildcost	Building costs no materials.
playerevents	Raids are chosen by each player's own progress rather than by which bosses have been killed on the server.
passivemobs	Enemies don't attack until provoked.
nomap	No map or minimap.
noportals	No portals. Not in the manual's list of -setkey values, but 1.0.16 accepted it and stored the key; it is the same key -modifier portals veryhard sets.

-preset: bundles of the above

Preset	What it set in our test
normal	Clears every modifier back to normal.
casual	Combat very easy, death penalty casual, resources more, raids none, portals casual, plus passive enemies and player-based raids.
easy	Combat easy, raids less.
hard	Combat hard, raids more.
hardcore	Combat very hard, death penalty hardcore, raids more, portals hard, no map.
immersive	No map, no portals, and fire hazards (wood can catch fire and spread).
hammer	No build cost, passive enemies, raids none.

Three rules, all of which we confirmed on 1.0.16:

• Put -preset first. A preset overwrites every modifier set before it. Started with -modifier raids none -preset hard, the world ended up with Hard's raids, not none. Put the preset first and the modifiers after it.
• Modifiers stay in the world. When we restarted that world with no modifier arguments at all, it kept every Hard key. Deleting an argument does not undo it. To go back, start once with -preset normal, which cleared all of them.
• Case doesn't matter. -preset Hardcore -modifier Combat VeryEasy worked the same as the lowercase form.

Where the World Is Saved

Without -savedir, the manual gives these default save folders:

System	Default save folder
Windows	%USERPROFILE%\AppData\LocalLow\IronGate\Valheim
Linux	~/.config/unity3d/IronGate/Valheim

Inside it, worlds live in worlds_local, and adminlist.txt, bannedlist.txt and permittedlist.txt sit directly in the save folder. With -savedir, the same layout is created under the path you give.

The 1.0 save format

Before 1.0, a world was two files in worlds_local: MyWorld.fwl (name and seed) and MyWorld.db (everything that changed). 1.0 introduced a new save system that, in Iron Gate's words, "splits world data across chunks" and is "designed to be resilient against mid-write failures". On 1.0.16 a world is a folder:

The number goes up as the server saves again. Copy or back up the whole MyWorld folder, never single files out of it.

An older world still in the two-file format is converted the first time 1.0 loads it. In our test, 1.0.16 loaded a world made by the last pre-1.0 server, and on its first save wrote the new OldWorld folder and moved the original pair aside as OldWorld_backup_ plus a date and time, .fwl and .db, in worlds_local. Keep that backup. The early 1.0 conversion lost the level and variant of items on item and armour stands; Iron Gate fixed it in patch 1.0.12, so a world converted on 1.0.12 or later converts correctly.

Moving a single-player world onto the server

• Stop the server.
• On your PC, open the same save folder (the Windows path above) and find the world in worlds_local: a folder with the world's name on 1.0, or the .fwl and .db pair for a world you haven't opened since 1.0.
• Copy it into the server's worlds_local. If the server already has a world with that name, move that one out of the way first.
• Set -world to the world's name, not its seed, and start the server.

The world's modifiers travel with it: they are stored in the world, so you don't need to repeat them as arguments.

Admins, Bans and the Permitted List

The server creates three text files in its save folder. Each starts with a comment line, and you add one player ID per line below it:

File	What it does
adminlist.txt	Players who can use the admin console commands.
bannedlist.txt	Players who can't join.
permittedlist.txt	A whitelist. As soon as one player is on it, everyone else is banned.

The manual gives the ID format as [Platform]_[User ID], case-sensitive, for example Steam_ followed by the player's 17-digit Steam ID. You can read a player's ID from the server log, or in game from the F2 panel. 1.0 also introduced IDs that start with V_; patch 1.0.12 fixed the ban list and permitted list so that both the new form and the old Steam_ form work.

An admin presses F5 in game to open the console. The admin commands the manual lists are kick [name], ban [name], unban [name] and banned (lists banned players).

Ports, Port Forwarding and Crossplay

Steam backend (no -crossplay)

Players connect straight to your server, so the ports have to be reachable from the internet. Forward UDP 2456 and 2457, or your -port and the port after it, to the server, and allow them in its firewall. In our test, 1.0.16 listened on the game port over UDP (IPv4 and IPv6) and on the next port over UDP (IPv4), and on nothing else that needs forwarding. The second port was open even with -public 0.

Crossplay backend (-crossplay)

The server sends its traffic through a relay server, so the manual says no port forwarding is needed. Players can join with the server's public IP and port, with a join code, or from the server list. They can't join with a local (LAN) IP or a loopback address such as 127.0.0.1, which catches out people testing from the same house. Without -crossplay only Steam players can join, so anyone playing on another platform needs a crossplay server.

Valheim is built for 1 to 10 players on a server, and Iron Gate's 1.0 FAQ says that hasn't changed with 1.0.

Classic Pitfalls

Skip the Hand-Editing

NodeMesh runs your Valheim server on your own PC or server, and its Config tab sets the start-line arguments for you as form fields: server name, world name, password, whether the server is listed, the difficulty preset, the five world modifiers (combat, death penalty, resources, raids, portals), the five checkboxes (no map, no portals, no build cost, passive enemies, player-based raids), the save interval, the number of backups and both backup intervals, and crossplay. NodeMesh puts -preset before the modifiers on the start line for you. You save, then restart from the same page.

NodeMesh starts the server with -savedir pointing at a save folder inside the server's own folder, so the world is in save/worlds_local and adminlist.txt, bannedlist.txt and permittedlist.txt are in save. Those lists are not Config-tab fields; edit them in the Files tab.