Your Valheim dedicated server crashes on startup: it starts, sits there for a few seconds, and closes immediately. Or it says Online and never lets anyone in. Either way it has almost certainly told you why, because Valheim writes the reason to its console before it dies. This article is the list of lines to look for, in the order they turn out to be the cause, with the fix for each.
One line matters more than any other. A healthy start ends with:
Game server connected
Until that prints, nobody can join, and if it never prints, one of the sections below is your problem. On our panel the live output is the Console tab, and it's the first place to look before you touch a single setting.
The password breaks a rule
This is the one we get the most tickets about, and it's the quickest to fix. On a public Valheim server the password has to be at least 5 characters, and it must not appear anywhere inside the world name or the seed. Not "can't equal the world name". Can't appear inside it. World called Midgard, password gard, and the server refuses to run. When it happens the console shows:
Error bad password:
and the process exits straight after, which from the outside looks exactly like a crash.
The fix is a longer password, or one that shares no run of letters with your world name or seed. The password and world name both live in the General group of the Manage tab, so a start that dies seconds after you changed either of them is nearly always this. Save, start, watch the Console.
A mod that wasn't built for 1.0
Valheim 1.0 shipped on 9 September 2026 on a newer Unity engine, so a mod compiled against the old build hooks into code that has moved. BepInEx loads, the plugin throws, and depending on what it patched the server either dies on the spot or boots into a half-working state where Game server connected never arrives. In the console it's a wall of red under the BepInEx banner, usually naming HarmonyX, a patch that failed to apply, or a method that no longer exists. Sometimes there's no crash at all. Just a server that never finishes starting.
Don't diagnose one mod at a time on a server that won't boot. Do it the boring way:
- Uninstall every mod.
- Start the server and confirm vanilla reaches
Game server connectedand someone can join. - Reintroduce mods in small batches, starting again after each batch, and stop when it breaks. The last batch holds the culprit. Split it and go again.
Anything with no release since 9 September 2026 is suspect until its Thunderstore page says otherwise, and honestly most of what breaks a 1.0 server is a mod whose author hasn't been back yet. With us the Mods tab's Installed list has Uninstall in every row's menu, and the loader's own log is game/BepInEx/LogOutput.log on the Files tab, last screen. We wrote up which mods have caught up and which haven't in Valheim mods after the 1.0 update.
The world file is corrupt or mismatched
A world that was cut off mid-save, uploaded incompletely, or written by a different build than the one now reading it will fail to load. Valheim is explicit about it:
World load failed mid-file. Exiting without save. Check backups!
or, a little deeper in a stack trace:
Exception while loading world ... Unable to read beyond the end of the stream
Both mean the same thing. The world data ends before the game expected it to, and the server won't guess at the rest. The only fix is a copy from before the damage, and "exiting without save" is the game doing you a favour: it hasn't overwritten anything, so your backups are still good.
Stop the server, put back the last known-good copy of the world, start again. If you uploaded this world from your own PC, re-upload it and copy the whole world folder this time, since a 1.0 world is a folder of .chunk files rather than a .db and .fwl pair. Our copies are on the Backups tab: Restore stays disabled until the server is fully stopped, and it writes the snapshot's files over the current ones. Anything the snapshot doesn't contain is left where it is, so on a 1.0 world delete the world folder first if you want an exact copy of the snapshot. Backups and restore covers what's in an archive and how far back you can go.
The world name points at nothing, or at a backup
Two versions of this.
A brand new world appeared. The World Name field changed, or picked up a typo, and Valheim did what it always does with a name it can't find: it made a fresh world called that. Your original is untouched. Stop, put the old name back, start.
The world went back in time. You picked a name ending in _backup_ and a date. That's the copy Valheim took before converting the world to the 1.0 format, and loading it puts everyone back to the day it was made. Same fix: stop, choose the real name, start.
Since 1.0 a world is a folder, and I'd check the name against the folder rather than trusting a suggestion. Our World Name field on the Manage tab only recognises the old .fwl files at the moment (known bug, fix pending), so its suggestions and its "no world called ... exists" notice can't be relied on for a 1.0 world. Look in config/valheim/worlds_local/ on the Files tab instead. The folder name is the world name.
It's not stuck, it's converting
If this is the first start after 1.0 on a world that existed before it, the server has a job to do before anything else. It takes a copy of the old .db and .fwl pair, then converts the world into the new folder format. On a big, old world that takes minutes, and the console shows very little while it happens. A server that looks hung at this point is usually working.
Don't stop it. Interrupting a conversion is one of the ways you end up in the corrupt-world section above. If it's been well past five minutes on a world that used to load fine, open a ticket rather than pulling the plug. Everything about that first 1.0 boot is in Updating your Valheim server to 1.0.
The disk is full
Valheim writes the world on a timer and keeps its own rotating backups next to it, so a server can run for weeks on a filling disk and only fall over when a save has nowhere to go. The tell is a start that gets through loading and then dies at the first save, or write errors near the end of the console. I couldn't find one exact log line Valheim prints for this, so treat any save-time error as a possible disk problem rather than hunting for a string.
Free the space, then start again. Old world folders you no longer use and the _backup_ copies from conversion are the usual weight, all visible on the Files tab. Nothing large and it still won't start? Open a ticket.
An update half-finished
Valheim patches often. There were three server builds in launch week alone (1.0.7 on 9 September, then 1.0.10 and the Steam-only 1.0.12 on the 11th), and an update interrupted partway leaves a game folder that's neither build. Missing file errors, a version that doesn't match what Steam says, a server that never reaches the BepInEx banner: all of that.
Run the update again and let it finish. A restart won't do it. Restarting never updates the server, which surprises people every single patch. The Game updates card on the Overview tab shows whether one is waiting, and its Update button stops the server, installs, and starts it again. Once it's on a clean build your players have to match it. A 1.0.7 server and a 1.0.12 client don't mix, but that shows up as a join failure rather than a crash, which is its own article.
A rough order for working through it
- Read the last thirty lines of the Console. That alone settles most cases.
Error bad password:means the password. Fix it and stop reading.- Red BepInEx or HarmonyX output means mods. Strip them, prove vanilla boots, reintroduce in batches.
World load failedorend of the streammeans the world. Stop, restore, start.- Nothing in the console and it's the first start since 1.0? Wait. It's converting.
- Died at a save? Check the disk. Died before BepInEx even loaded? Run the update again.
The wider troubleshooting guide covers what happens once the server is up, and common issues is the shorter list. If you've been through the Console and it still means nothing, open a ticket with what changed since it last worked and the last screen of output. On Valheim server hosting with us that's usually one round trip.