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Valheim / Graphics & performance

Valheim: dedicated server causes high CPU load on the gaming PC

Players hosting a Valheim server on their own gaming PC sometimes saw unexplained high CPU load until October 2026. Iron Gate found the cause: when the client ran with V-Sync enabled on the same computer, the dedicated server could run at an uncapped frame rate and burn massive amounts of CPU time. Patch 1.0.20 on October 15, 2026 fixes this.

Updated: ·2 min read·Windows / PC
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STRAIGHT TO THE SOLUTION

Start here

01Symptom↓02Step 1: narrow down the case↓03Step 2: update server and client↓
01

Symptom

  1. Fans spin up, game FPS drop, and Task Manager shows the valheim_server process using a lot of CPU even with few players connected.
02

Step 1: narrow down the case

  1. In Task Manager, compare the server's CPU load once with the game closed and once with it running.
  2. Check: if the load only rises while the game runs with V-Sync on the same PC, the described bug fits.
03

Step 2: update server and client

  1. In your Steam library under Tools, update the Valheim Dedicated Server application to 1.0.20 or later, and the game too. Stop the server with Ctrl+C in the console window first.
  2. Iron Gate notes that closing via the X can leave the server running in the background. Check Task Manager for leftover processes before restarting.
04

Step 3: keep your start script

  1. Steam resets start_headless_server.bat on updates. Iron Gate recommends editing a copy; after updating, check that name, world, port and password are still correct.
05

Stopgap for older builds

  1. If you cannot update the server immediately, temporarily disable V-Sync in the client. This is inferred from the patch note, not an official workaround.
06

If the load stays high

  1. After the update, high load can have other reasons, such as many players, large bases or mods. Test a backed-up copy of the world without mods and compare again.

Related guide

Sources and current status

Frequently asked questions

Does this affect a server on a separate machine?

According to the patch note, only when the client runs with V-Sync on the same computer.

Why is the server still running after closing it?

Iron Gate recommends stopping the server with Ctrl+C; the X can leave it running in the background.

Will the update delete my server world?

No, the world is stored in the save folder. Back it up before every update anyway.

How do I recognise the server process?

In Task Manager it is called valheim_server. The start script start_headless_server.bat launches it on the line that begins with "start valheim_server".

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