How to Fix a Factorio Server That Keeps Crashing
Factorio server crashes are usually one of a handful of known causes — a version mismatch, a mod desync bug, a megabase UPS collapse, or bad RAM. Here's how to diagnose and fix each one.
Server and client running different Factorio versions
Factorio's simulation is deterministic and extremely version-sensitive — even a patch-level mismatch between server and connecting clients causes an immediate desync that looks like a crash. Fix: keep the server and every client on the exact same version before anyone connects.
A mod with a determinism bug causing desync
Mods that don't handle Factorio's deterministic simulation correctly are a far more common desync cause than core-game bugs. Fix: if you're desyncing with mods enabled, disable them one at a time to isolate which mod is responsible.
Late-game megabase UPS collapse
A sprawling megabase with heavy biter bases, long belts and dense inserter counts can push UPS (updates per second) down far enough that the server starts timing out connections, which players experience as random crashes or disconnects rather than visible lag. Fix: profile with the in-game UPS/timing display and optimize or split the worst-offending production lines before they drag the whole server down.
Bad RAM producing wrong simulation results
If you're desyncing with no mods on the latest version, failing memory on the physical machine can cause the simulation to compute wrong results occasionally, which reads as a random, unexplained crash. Fix: run a memory test (memtest86) on the host if other causes are ruled out.
Outdated server software
Running an old server build against newer clients — or just an old build in general — causes stability issues, unexpected behavior, and sometimes outright failure to start. Fix: update the server to the latest stable Factorio release and keep it there.
Corrupted save from a bad shutdown
Killing the server process instead of a graceful stop during an autosave can corrupt the save file, crashing on the next boot. Fix: restore from the automatic save or backup, and always allow a graceful shutdown.
FAQ
Why does my Factorio server desync as soon as someone joins?+
Can a megabase actually crash the server?+
How do I find which mod is causing a desync?+
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