Resolve Factorio mod and startup-setting mismatches
A Factorio client can have the right mod names and still fail to match the server. Compare the exact versions and startup settings before replacing files. This guide covers a mismatch when joining an existing factory, with the aim of preserving its save and agreed mod set.
Capture the mismatch first
Record the full game version on the client and server. Save the join error and the first relevant server-log message. Make a list of enabled mods with their versions, including the expansion-related components your game uses. A name-only list misses the information needed to reproduce the session.
Download a recovery copy of the current save and mod configuration before changing the server. Treat a mod migration as a change to the factory: removing a content mod can affect entities or recipes when the save loads. Do not accept an automatic server-side change simply because one client has a different collection installed.
Synchronise the client to the agreed server
- Confirm that the server’s current mod set is the intended one. If the whole group lost access after maintenance, inspect the server change first.
- Use Factorio’s offered multiplayer mod synchronisation when joining. The upstream modding guide explains that it selects the server’s exact mod versions and can synchronise startup settings.
- Allow the client to complete any required game restart. Recheck the enabled set before reconnecting.
- If a download fails, verify account access to the official mod portal and the named mod version. Do not fetch an executable or altered ZIP from an unrelated download site.
- Compare the next error with the original. A resolved mod mismatch can reveal a separate game-version or authentication issue.
Investigate a server-side mismatch
If startup logs report missing dependencies or incompatible mods, stop the instance and compare the installed files with the recorded configuration. Look for a partial upload, duplicate version files or a template that updated the game but retained an older mod set.
Keep the official mod ZIP files in the form expected by Factorio. Do not unpack and edit a mod to force it to accept another version. Local modifications can change checksums even when the visible mod version remains the same.
For a planned change to startup settings, test a copy of the save with the exact proposed mod set and game version first. Use that copy to check whether the factory loads, key production chains remain present and a second client can join.
Recover without mixing states
If the proposed set fails, restore the saved mod configuration and compatible save as a matched pair. Avoid loading a save already migrated by a newer mod set with older files and assuming it will reverse those changes.
Send support the exact game version, mod names and versions, mismatch text and a redacted startup excerpt if you remain blocked. Keep portal tokens and account credentials private. Tell the group which combination is the approved baseline so another client update does not restart the same investigation.