Valheim Server Not Starting: Errors and Fixes

Where to see the error

On your PC, in the black window that start_headless_server.bat (or your copy) opens. When the server is ready it says “Game server connected”: if the window closes before that or never reaches that line, what matters are the last lines. Since the window closes on its own, it's worth saving it to a file: add -logFile followed by a path (for example, -logFile "C:\valheim-log.txt") to the startup line and read the end of that file.

If you have mods, BepInEx also writes its own log, BepInEx/LogOutput.log, in the server folder: it shows which mod didn't load and why. On a rented server, all of this is in the panel's console.

The password: fewer than 5 characters or inside the name

It's the number one cause. On a public server, Valheim won't start if the password has fewer than 5 characters or if it's contained in the server name (-name) or the world name (-world). “Vikings” as the world and “vikings1” as the password counts as contained; “mead42” doesn't.

Also avoid spaces and quotes in the password: on the .bat line each value goes in quotes, and an extra space or quote breaks the line. Change it, save the file and start again. Where each thing goes on that line, in creating a Valheim dedicated server on your PC.

It starts, but with a new, empty world

It's not that it won't start: it can't find your world and creates another one. -world loads the world with that name and, if it doesn't exist, creates it. It has to match the world folder inside worlds_local letter for letter (including capitals), or the name of the .db and .fwl files if it's a pre-1.0 world. Your world hasn't been deleted: it's still there, next to the new one.

1. Stop the server

   With Ctrl+C in its window, not with the X.

2. Check what the folder is called

   In worlds_local, inside %USERPROFILE%\AppData\LocalLow\IronGate\Valheim on Windows or ~/.config/unity3d/IronGate/Valheim on Linux (unless you use -savedir). If the world is in the Steam Cloud, move it to local first from the game's manage saves menu.

3. Copy that name into -world

   Exactly as it is, in quotes. The folder has to be directly inside worlds_local, not inside another folder (it happens when unzipping a .zip).

4. Start it and check

   The console has to load your world, not generate one. Once you're sure, delete the empty world that was created by mistake.

The port is in use

The server uses the port you give it with -port and also the next one (2456 and 2457 by default). If another program or another server already has them, the new one can't use them. The most common culprit is Valheim itself: the official manual warns that if you close the window with the X, the server can keep running in the background. Open Task Manager, look for valheim_server.exe, end it and start again. From now on, always stop it with Ctrl+C.

If you have two servers on the same PC, space their ports two apart (2456 and 2458). And if both run with crossplay and the same port, the manual asks for a different -instanceid for each one. Everything about ports, in Valheim ports.

A BepInEx mod that isn't for 1.0

Valheim has no official mods, and with 1.0 (9 September 2026) many stopped working until their authors updated them. If the server stopped starting right after installing a mod or after a game update, start here (what changed with 1.0).

1. Back up the world

   Before removing mods: some save things in the world.

2. Read BepInEx/LogOutput.log

   Look for the first error: it usually names the mod that fails or the dependency it's missing.

3. Check the mod's date on Thunderstore

   If its latest version is before 9 September 2026, it wasn't made for 1.0. Update it or remove it.

4. Remove the last one you added

   Take it out of BepInEx/plugins and start. If you don't know which one it is, remove them all and add them back a few at a time.

A pre-1.0 world

Since 1.0, each world is a folder. An old world (a .db and a .fwl) still works: the first time it loads it, the game makes a backup and converts it. For that it needs both files, with the same name and from the same date; a .db without its .fwl, or from different dates, causes problems. If the conversion stops halfway or something doesn't load, go back to the backup the game made (how to recover a world).

Keep the server up to date: patch 1.0.17 fixes a rare bug that could delete every item in parts of the world when splitting a large file of the new save format into smaller ones.

Linux: missing packages or the GLIBC version

If on Linux it closes without loading anything, check the libraries first. The official manual asks for the libatomic1, libpulse-dev and libpulse0 packages, and at least GLIBC_2.29 and GLIBCXX_3.4.26. If your system is older, the manual itself suggests running it with Docker.

Memory or disk

If the server starts and crashes when loading the world or when someone joins, especially with lots of mods or a heavily explored world, it's usually memory: for a group without mods about 4 GB is enough; with mods or huge bases, 6 GB (how much RAM it needs). If the server is on the PC you play on, count what the game uses too.

With a full disk, the server can't save. What grows most over time, besides the world, are the backups the game itself keeps next to it (-backups sets how many it keeps): delete the old ones or keep fewer.

On NapNodes

Ports aren't your problem: each server has its own, shown on the “Address to play” card. And with “Update the game on start” turned on (it comes that way), the server updates itself when it starts.

1. Check the “Console”

   On your server, the “Console” shows what the game says on startup. The first time, installation takes about 5 minutes: if it's still installing, it isn't broken.

2. The password already comes right

   It's generated automatically and you'll find it in “Settings” → “Password to join”, with “Copy”. If you change it, the panel won't let you save one with fewer than 5 characters or one contained in the server or world name.

3. The world, with its folder's name

   The “World” setting in “Settings” has to match the folder in worlds_local (in “Files”, inside .config/unity3d/IronGate/Valheim). If you uploaded a world as a .zip, check after “Decompress” that the folder didn't end up inside another one.

4. Remove the last mod

   In “Mods”, “Installed” tab, remove the last one you added and press “Restart”. The panel installs BepInEx on its own and only turns it on if there are mods.

5. If the world is damaged

   The panel's backups are in “Backups”; the game's own, in worlds_local. The free server has no panel backups, and its disk is 5 GB: you get an email at 80% and at 95%.

6. If none of this fixes it

   Open a ticket in “Help” with the last lines of the console. As a last resort, “Reinstall server”, at the bottom of “Settings”, runs the game installation again (make a backup first).

Frequently asked questions