Check if your Valheim server is online
Valheim occupies a short block of consecutive UDP ports, and the number you enter in the game is not the one that responds to queries.
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The ports Valheim uses
Players join on the game port, but queries are answered one port higher. So forwarding a single port gives you a server friends can join and no checker or listing can find. Both ports must be UDP.
Every port a default Valheim install uses
With the game port left at 2456. If you changed it with -port launch argument, the other ports move with it.
| Port | What it is for |
|---|---|
| 2456 UDP | Game trafficRequired The port you actually connect to. |
| 2457 UDP | Steam queryRequired How Valheim advertises itself and how the in-game browser finds you. Forward it, or your friends must join by IP every time. |
| 2458 UDP | Legacy Steam portOld versions only Required by builds from 2021 and earlier. Harmless to include, unnecessary on current versions. |
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Still offline? Try this
Forward the game port together with the next one up and test again. A server configured not to be publicly listed will not reply to queries at all — that is deliberate, not a fault, and anyone with the address can still connect directly.
What a Valheim server needs to run well
- Memory, 5 players
- 6 GB
- CPU cores
- 2+
- Disk
- 5 GB+
Light CPU load; the ten-player cap keeps it modest whatever else is going on.
What the checker asks a Valheim server
Valheim answers status requests the way most Steam games do: a short UDP query sent to the port one above the game port, which replies with the server name and current player count. The checker sends exactly that query. If your server answers it, so will every server list and favourites entry that looks for Valheim servers.
When there is no answer, the cause is nearly always on the network side rather than in the game: the query port is not forwarded, the server is started with -public 0, or the firewall on the machine running the server is dropping UDP.
Why the result can differ from what you see at home
The check runs from our server, not from your browser, so it reaches your server the way a friend in another city would. That is the useful test. Joining from a PC on the same network as the server can work even when nothing is forwarded, because the traffic never leaves your router, and plenty of routers will not route a connection to their own public address back inside at all. A server that only works at home has not been tested yet.
Online but nobody can join
If the checker finds the server but players are turned away, look at versions before ports. Valheim clients will not join a server running a different game version, and the dedicated server is a separate Steam app (896660) that does not update itself when the game does. After every Valheim patch, update the server through SteamCMD and restart it.