Old save won’t load after the Build 42 update?

Before switching: preserve the original

Stop testing on your only copy. Keep a separate backup of the save and record the version it last worked on, plus any mods it depended on. Do not delete old saves as a routine troubleshooting step.

That warning has a practical reason: a player report describes deleting Build 41 saves while investigating a Build 42 crash, then discovering that Build 41 still ran. It is a cautionary example, not proof of the cause of your error. Read the player troubleshooting case ↗

Which branch should you choose?

• Your last working game was Build 41: choose legacy41.
• Your save was made on Unstable 42.19: choose 42.19.
• Your save already belongs to 42.20: these legacy choices are not a general fix for its loading errors.

If you do not know the save’s version, establish that first instead of cycling through branches at random.

Change the version in Steam

1. Close Project Zomboid.
2. In the Steam Library, right-click Project Zomboid and open Properties.
3. Open Game Versions & Betas and select the matching branch above.
4. Let Steam finish the version change. Launch the game and check the displayed version before loading your saved world.

Official branch instructions ↗

Still failing on the matching version?

Separate a version mismatch from a crash, a mod dependency or a damaged save. Record the exact error and whether a new game on that same version starts successfully. Keep that test separate from the original world.

For multiplayer, ask the host which branch the server runs before changing your client. Choosing a solo legacy branch does not configure a server for you.

If the branch matches but the problem remains, use the developer’s support link in the release announcement. Include the build number, exact error and whether the issue is solo or multiplayer. This guide does not promise to recover deleted or corrupted saves.