First check who is lagging. One player only: it is their game or connection. Everyone at the same moment, every 30 minutes: the world save (see World saves). Everyone near one player: that player holds the area, so ask them to leave and come back. Also look at the CPU load and Memory load tiles at the top of the server page: if either is full, see out of memory.
Much of Valheim lag comes from the players’ games, not the server’s machine. A Valheim server passes messages between players. Each player’s own game runs the part of the world around that player. So a slow computer or a poor connection on one player’s side can make everyone near them lag.
Who runs the world
Per the Valheim wiki, the server relays traffic and the players’ games claim the role of running each area. The player who holds an area does the work for everyone standing in it.
If that player’s computer is overloaded, or their connection is poor, everyone in the area sees delays. Opening chests, opening doors, buildings falling and trees falling all feel slow.
Fixes:
- Let the player with the best computer and connection enter a new area first.
- If one area is slow, ask the player who was there first to leave the area and come back. The wiki describes this as a way to hand the role to someone else.
- Close heavy programs on the slow computer.
World saves
The server saves the world on a timer. While it copies the world in memory, relaying is on hold. The wiki says this usually takes 20 to 300 milliseconds, then writing to disk continues in the background. Players feel a short pause.
The game’s own default is a save every 30 minutes. To check or change it:
- Open the Config Editor page and the Server settings source.
- In the Saving group, read Save every (minutes) (1). It takes 5 to 120.
- Choose Save, then choose Restart at the top of the server page.
- Save every (minutes)
- Crossplay
A longer interval means fewer pauses, and more play lost if the server ever stops without saving. See the save interval. The wiki also says a save is easier on the server when the group does not split up and load many areas at once.
New ground
The wiki says making the world is heavy on the processor. When someone enters an area for the first time, the server generates it then. Every new area costs the server that work.
Crossplay
With crossplay on, players do not connect to the server directly. Their traffic goes through a relay. The wiki says the extra step adds delay and makes the connection less steady, so players are more likely to see lag, timeouts and disconnects.
To change it, use Crossplay (2) in the Server group of the same Server settings source. Turning it off means players on Xbox and Game Pass can no longer join. See crossplay servers.
Mods
A modded server does more work. The wiki says modded servers need better hardware. On the Mods page, Load mods switches them off without removing them. Turn it off for a test: if the lag stops, a mod is the cause.
Desync
Desync means two players see different things in the same place. The wiki ties it to the same causes as lag, and says to disconnect and join again.
If it does not work
- Lag for one player only. It is most likely on their side, in their computer or connection. If they hold an area, others near them lag too.
- Lag at the same interval. Match it to the save interval above.
- The server runs out of memory. See out of memory.
- Lag and nobody can explain it. Send support the server name and the time it happened.
More about the game: Valheim servers.