Valheim Server Troubleshooting Guide

Symptoms:

• Players cannot connect to server
• "Failed to connect" message appears
• The game says the server is on an older version: check which branch the server runs (Stable or public-test) in the panel before anything else, see Switch Version.
• Server shows in browser but connection times out

Solutions:

1. Check Port Forwarding: On the Steam backend, forward the server's port and the one above it (2456-2457 by default) on your router. A server started with -crossplay needs no forwarding at all, because its traffic goes through a relay.
2. Verify Firewall Settings: Add exceptions for Valheim server executable in Windows Firewall or configure iptables on Linux.
3. Test Local Connection: On the Steam backend, try connecting from a device on the same network to rule out internet issues. This test does not work on a crossplay server: Iron Gate's server manual says a crossplay server cannot be reached on a local or loopback address, so use its join code or public IP instead.
4. Check Server Status: Verify the server process is running with netstat -tulpn | grep 2456 (Linux) or Resource Monitor (Windows).

Symptoms:

• Server doesn't appear in Steam server browser
• Direct IP connection works but browser doesn't show server
• If the browser or a query tool reports the server offline while players can still join by direct IP, join by direct IP; the listing comes back on its own once a player is in.
• Server visibility set to "Public" but not listed

Solutions:

1. Enable Steam Networking: Ensure -public 1 is set in server arguments.
2. Check Query Port: Verify port 2457 is open and accessible (used for Steam queries).
3. Wait for Registration: a freshly started server can take several minutes to appear in the list.
4. Join it directly meanwhile: in Valheim, Join Game, Add server, then the address and port (or the join code on a crossplay server).

Symptoms:

• Delayed player actions and movements
• High ping for all connected players
• World saving causes temporary freezes
• Players see different states (doors open/closed, items in different positions)
• NPCs or players "skipping" across the screen

Understanding the Root Cause:

Valheim uses a "Peer-to-Peer within Dedicated Server" hybrid model. Physics calculations are done client-side, and the first player to enter an area becomes the "Zone Owner" responsible for synchronizing that zone. If that player has poor connectivity, everyone in that zone experiences issues.

Solutions:

1. Zone Owner Strategy: Have the player with the best connection lead the group into bases and new areas.
2. Install Better Networking mod: This mod increases data rate limits and adds compression. See our Better Networking guide.
3. Use Wired Connection: Switch from WiFi to Ethernet; this alone fixes many desync issues.
4. Lower Steam Pings: In Steam Settings → In-Game, reduce "In-game server browser pings per minute" from 5000 to 250.
5. Disable Crossplay: If all players are on Steam, disable crossplay for better performance.
6. Reduce Building Density: every piece in a loaded area is data the zone owner has to keep in sync. In 1.0.17 the server runs each Steam connection at a fixed 150 KB a second and only queues more world data for a player while less than 10 KB is still waiting, so one huge base in one area is where that ceiling shows first.
7. Check the Save Interval: the default -saveinterval is already 1800 seconds. A big world can stall for a moment while it saves; saving less often makes the stalls rarer but loses more progress if the server crashes.

Symptoms:

• Server process using excessive CPU (90%+)
• Memory usage constantly increasing
• Server becomes unresponsive over time

Solutions:

1. Know the Player Cap: vanilla Valheim has no player-count setting; the server turns away an eleventh player with "disconnected due to server is full" in its log. More than 10 needs a mod.
2. Regular Restarts: Schedule daily server restarts to clear memory leaks.
3. Monitor with Tools: Use htop (Linux) or Task Manager (Windows) to identify resource hogs.

Symptoms:

• World fails to load
• Characters or structures missing
• "Failed to load world" error message

Solutions:

1. Restore from Backup: Use Supercraft's automated backups, or the game's own: a 1.0 world keeps automatic backup folders named WorldName_backup_auto-... next to it, and older worlds have .db.old and .fwl.old copies.
2. Verify File Permissions: Ensure server has write access to world save directory.
3. Check Disk Space: keep free space well above the size of the world folder.
4. Find the last good copy: the free Valheim World Recovery tool reads your worlds folder in the browser and, for worlds last played before 1.0, pairs every .db with its .fwl, ranks the copies by save time and integrity, and hands back the newest intact pair ready to upload.

Symptoms:

• Character items missing after server transfer
• Skills reset or decreased
• Character file corruption errors

Solutions:

1. Back up characters on each player's PC: a vanilla dedicated server does not store characters. When it saves, it tells every connected player's game to save that player's own character file, which stays in characters_local on their machine.
2. Know what a character keeps per world: the file holds a separate map, bed spawn point, logout point and death point for every world, keyed to the world's own ID rather than its name. Renaming a world keeps them; a new world with the same name and seed starts with a blank map.
3. Moving between servers is safe: the same character joins any server, carrying its inventory and skills, which is exactly why some community servers use a mod to keep characters on the server.
4. Manual Restoration: Replace corrupted .fch files with backups.

Symptoms:

• Progress lost after server restart
• World reverts to earlier state
• Buildings or items disappear
• "World Saved" message never appears

Understanding the Issue:

Dedicated servers autosave every 30 minutes by default. If the server shuts down ungracefully, all progress since the last autosave is lost.

On 1.0 there was one more cause, fixed in patch 1.0.17 on 6 October 2026: a rare bug could erase all objects in parts of the world when one large world save chunk file was split into smaller ones. If whole areas lost their buildings at once, rather than the last half hour of changes, update the server to 1.0.17 and restore a world backup made before the loss.

Solutions:

1. Force Save Before Shutdown: As an admin (your ID in adminlist.txt), press F5, type save, and wait for the "World saved" message before stopping the server. Anyone else gets "You are not admin", and only their own character is saved.
2. Check Save Folder Location: After updates, Iron Gate moved saves from worlds to worlds_local. Ensure your server points to the correct folder.
3. Verify Write Permissions: Ensure the server process has write access to the save directory.
4. Check Disk Space: Insufficient disk space prevents saving. Keep free space well above the size of the world.
5. Avoid File Conflicts: Never run client and server on the same world file simultaneously.
6. Check for Read-Only Files: Ensure the world folder (1.0) or the .db and .fwl files are not marked read-only.

Save File Migration (Post-Update Fix):

# If world disappeared after update:
# 1. Backup both folders first!
# 2. Copy files from old to new location:
cp ~/.config/unity3d/IronGate/Valheim/worlds/YOURWORLD.* \
   ~/.config/unity3d/IronGate/Valheim/worlds_local/

Symptoms:

• Server boots fine with an empty worlds_local/ directory (creates a fresh world).
• Server hangs on "Loading world" or crashes when an existing world (a 1.0 folder, or .db / .fwl files) is present.
• The world played fine on this same server hours or days ago.

Most common causes ranked:

1. Crashed mid-save leaving a corrupt active file. The previous shutdown happened during a save write. The .db on disk is partially written.
   Fix: Stop the server. Rename current .db to .db.broken and .fwl to .fwl.broken. Restore the most recent .db.old and .fwl.old backup pair as the active files. On a 1.0 world: rename the WorldName/ folder to WorldName_broken/ and the newest WorldName_backup_auto-.../ folder to WorldName/. Start the server.
2. File ownership/permissions changed. Common after a deploy script or container rebuild, where the world files are owned by root but the server runs as a non-root user.
   Fix: chown -R valheim:valheim worlds_local/ and ensure chmod 644 on the world files (the .db/.fwl pair, or everything inside the 1.0 world folder).
3. Mod added that doesn't load on dedicated server. Server tries to deserialize world data with a BepInEx mod that crashes during load.
   Fix: Move BepInEx/plugins/ aside temporarily. Start server. If the world loads, reintroduce mods one at a time to find the culprit.
4. Version mismatch between save format and server build. Save file was written by a newer Valheim build than the server is now running (e.g., container image got pinned to an older version).
   Fix: Check the build ID per the INCOMPATIBLE_VERSION article. Update the server to match the save's format.

Diagnostic order (Linux):

# Check ownership
ls -la ~/.config/unity3d/IronGate/Valheim/worlds_local/

# Check active backups available
ls -la ~/.config/unity3d/IronGate/Valheim/worlds_local/ | grep -E '\.old$'

# Check journalctl for the actual crash line
journalctl -u valheim -n 100 | grep -iE 'error|exception|abort|deserialize'

The line that gives you the actual answer is usually within 20 lines of "Loading world" in the log. If it says "deserialize" or "Failed to load", you have a corrupt save → restore backup. If it says "permission denied", you have ownership issues. If it says nothing and just hangs, you probably have a mod blocking load → remove plugins.

Symptoms:

• Xbox/Game Pass players cannot see or join Steam-hosted games
• "Unable to join crossplay game" error
• Connection works for some platforms but not others

Solutions:

1. Enable Crossplay Flag: Add -crossplay to server launch parameters.
2. Use Join Codes: Steam and Xbox players should use the Join Code from the pause menu rather than server browser.
3. Install VC Redist: Steam doesn't install VC Redist 2015-2022 with Valheim. Download from Microsoft.
4. Check Parental Controls: Xbox parental controls may block crossplay features.
5. Host with crossplay on: a Steam player can host a world for Game Pass and console friends with Start Server and Crossplay ticked, but the world is only reachable while the host plays. A dedicated server keeps it up around the clock.

Symptoms:

• Server crashes on startup with mods enabled
• Players cannot connect due to mod mismatch
• Game features broken after mod installation

Solutions:

1. Verify Mod Versions: Ensure all mods are updated to latest versions compatible with Valheim version.
2. Check Dependencies: BepInEx loads mods in the order their declared dependencies require, so a missing dependency is the usual culprit. doorstop_config.ini only points the game at BepInEx; it holds no load order.
3. Test Mods Individually: Disable all mods, then enable one at a time to identify conflicts.
4. Use BepInEx Logs: Check BepInEx/LogOutput.log for mod loading errors.

Symptoms:

• Mods not loading despite BepInEx installation
• Server starts but mod functionality missing
• BepInEx console not showing on server start

Solutions:

1. Verify Installation Path: BepInEx files should be in Valheim root directory, not subfolders.
2. Check File Permissions: Ensure server has execute permission for BepInEx executables.
3. Update BepInEx: Use latest BepInEx version compatible with server Valheim version.
4. Review Configuration: Check BepInEx/config/BepInEx.cfg for correct settings.