Factorio: Fixing Multiplayer Desyncs
"Desynchronization" happens when your client thinks the game state is X, but the server says it is Y. Factorio is deterministic; if 1+1 doesn't equal 2 for everyone, the game kicks you to reload the map.
1. The Loop
If you join, play for 10 seconds, get dropped, and reload... you are in a Desync Loop. This is usually caused by a Mod or Corrupt Map Data.
2. The Report
Factorio generates a `desync-report` zip file. This contains the smoking gun for developers or modders.
3. Heavy Mode
A debug mode that forces the game to double-check every calculation. Useful for finding WHICH mod is lying.
Common Causes & Fixes
1. Mod Mismatch (The #1 Cause)
Even if version numbers match, a "local" modification to a mod's Lua files will cause desyncs.
- Fix: In the server browser, check **"Sync mods with server"**. This forces your client to download the exact zip files the server is using.
- Fix 2: Delete your `mods` folder locally and let Steam/Game re-download them fresh.
2. The "Remote View" Bug (Space Age)
In Factorio 2.0 (Space Age), using Remote View on large planets can trigger desyncs if the server optimization settings differ from the client.
- Fix: Ensure both Server and Client are running the **Exact Same Version** (e.g., 2.0.15). Do not mix Stable client with Experimental server.
3. Analyzing the Desync Report
When you desync, a folder is created in your Factorio directory (`/archive/desync-report-...`).
- Open the `level-tick-xxxx.dat` info (requires technical knowledge).
- Easier: Upload the report to the **Factorio Forums** -> **Bug Reports**. The developers are incredibly active and will often tell you exactly which mod caused it.
Debugging with Heavy Mode
If you are a server admin and the map keeps crashing users:
- Start the server with the flag: `--check-consistency`.
- Or use the console command:
/c game.force_crc()to force a check immediately. - If you suspect a specific mod, try disabling recently added script mods (mods that change game logic, not just add items).
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