Symptoms:

• Players cannot connect to server
• "Failed to connect" message appears
• Server shows in browser but connection times out

Solutions:

1. Check Port Forwarding: Ensure ports 2456-2458 (TCP/UDP) are properly forwarded on your router.
2. Verify Firewall Settings: Add exceptions for Valheim server executable in Windows Firewall or configure iptables on Linux.
3. Test Local Connection: Try connecting from a device on the same network to rule out internet issues.
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
• 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: Steam server browser can take 5-15 minutes to register new servers.
4. Use Steam Console: Type openserverbrowser in Steam client console to refresh browser.

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: Large bases with 5000+ pieces overwhelm the 64KB/sec data cap.
7. Optimize Save Interval: Increase -saveinterval to 1800+ seconds for large worlds.

Symptoms:

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

Solutions:

1. Limit Player Count: Reduce -players setting to match server capabilities.
2. Disable Console: Remove -console argument if not needed.
3. Regular Restarts: Schedule daily server restarts to clear memory leaks.
4. 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 manual .old backup files.
2. Verify File Permissions: Ensure server has write access to world save directory.
3. Check Disk Space: Ensure adequate free space for world saves (minimum 500MB).
4. World Repair Tools: Consider using community tools like Valheim World Editor for recovery.

Symptoms:

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

Solutions:

1. Backup Character Files: Regularly backup characters folder from server.
2. Use Consistent World Names: Character data is tied to specific world names.
3. Avoid Cross-Server Transfers: Character files may not be compatible between different server configurations.
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.

Solutions:

1. Force Save Before Shutdown: As an admin, press F5, type save, and wait for "World Saved" message before stopping the server.
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. Maintain at least 500MB free.
5. Avoid File Conflicts: Never run client and server on the same world file simultaneously.
6. Check for Read-Only Files: Ensure .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:

• 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. Dedicated Server Required: Steam and Game Pass PC players cannot join each other's games directly - use a dedicated server.

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 Load Order: Some mods require specific load order in doorstop_config.ini.
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.