Project Zomboid Server Version Mismatch: How to Update Your Server
When a Project Zomboid patch comes out, Steam updates your game straight away, but the server stays on the old version until someone updates it. Until then, nobody with the new game can join. It's fixed in a few minutes: it's almost always the server lagging behind, sometimes your Steam on a beta and, now and then, a mod.
Which version you have and which one the server has
Your version is shown at the bottom of the game's main menu (for example, 42.21). When you try to join, the version mismatch error shows both: the server's and your client's. Since 42.21, the game also warns you clearly when they don't match.
If the server's is lower, go to case 1. If yours is different from the normal Steam version, go to case 2.
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Case 1: the server is behind
Before updating, back up the world: small patches don't usually touch saves, but big jumps do (from 41 to 42, or from unstable 42 to 42.20, saves don't carry over: Build 42 vs Build 41).
If it's the Steam dedicated server
Close the server and open Steam: “Project Zomboid Dedicated Server”, under “Tools”, updates like any game. If it doesn't, right-click → Properties → “Installed Files” → “Verify integrity of game files”.
If you installed it with SteamCMD
Run the server download again (app 380870) with validate, and start it.
If it's a rented server
Look in its panel for the option to update the game, or ask them to update it. On NapNodes, see below.
Case 2: you're on another branch
If you ever tried the unstable branch, or legacy41 for Build 41, you may still be on it. In Steam, right-click Project Zomboid → Properties → “Betas” (in the new Steam, “Game Versions & Betas”) and choose “None” to go back to the normal version. Or, if the whole group and the server are on another branch on purpose, switch to that one.
Case 3: it's a mod
If the error mentions a Workshop item (“Workshop item version is different than server's”), it isn't the game but a mod that has been updated while the server still has the old version. Restarting the server fixes it: it downloads the new one on start. Other mod errors are in the Workshop mods guide.
To find out before it happens whether any mods have a new version, an admin can type /checkModsNeedUpdate: the result goes to the server log.
On NapNodes: let it update itself
Turn on updating
In “Settings”, in the “On start” group, turn on “Update the game on start”. From then on, if there's a new version, it's downloaded on start (it takes a bit longer).
Make a backup
In “Backups”, before a big patch. The free server has no backups: in “Files”, select the world folder (in .cache/Saves/Multiplayer), then “Compress” and “Download”.
Restart
Click “Restart” and watch the “Console”: you'll see it download the update and start.
So you never have to think about it again
With a plan, schedule a daily restart in “Advanced settings” → “Schedules” at a time when nobody's on (how to create the schedule (in Spanish)): with updating turned on, the server catches up every day and frees memory too.
Frequently asked questions
Why does Project Zomboid say the server version doesn't match?
Because your game and the server are on different versions: almost always, Steam has updated you and the server is still on the previous one. Update the server and restart it. If you still can't join, see the other causes.
How do I update my Project Zomboid server?
The Steam dedicated server updates from Steam like a game; with SteamCMD, by downloading app 380870 again. On NapNodes, turn on “Update the game on start” in “Settings” and restart.
How do I check which Project Zomboid version I have?
It's shown at the bottom of the game's main menu. The server's version is given by the error itself when you try to join.
Will I lose my save when I update the server?
With small patches, normally not. With big jumps (from Build 41 to 42, for example), yes: the old world won't open. Always make a backup first.
How do I leave a Project Zomboid beta?
In Steam, right-click the game → Properties → “Betas” (or “Game Versions & Betas”) and choose “None”. Steam downloads the normal version.
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