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Project Zomboid Build 42 server branches: Stable, Pre-Release, 42.21 and Build 41

Which Steam branch a Project Zomboid server should follow: Stable, pre-release, 42.21 for modded worlds or legacy41 for Build 41, and how to switch safely.

Last checked 12 November 2026

Short answer

A Project Zomboid server follows one Steam branch, and every player has to be on the same one. Stable is Build 42 and suits most groups. pre-release gets the next update first, 42.21 keeps the previous Stable for worlds whose mods are still catching up, and legacy41 is Build 41. Pick the branch your group plays, set it on the server and in each player's Steam, and take a copy of the world before you switch.

The four branches to choose from

These are the names Steam uses, for the dedicated server and for the game. Type them exactly as shown.

Project Zomboid's Steam branches, what each holds and who it suits
Branch	What it holds	Who it suits
Stable (`public`)	What it holdsBuild 42. It became Stable with 42.20.0 on 29 July 2026, and 42.22.2 arrived on 9 November 2026.	Who it suitsMost groups. It is what Steam installs by default, for players and servers.
`pre-release`	What it holdsThe next update, for at least a week before it becomes Stable. It replaced the unstable branch on 27 October 2026. On 12 November 2026 it held the same build as Stable.	Who it suitsGroups who want to try an update early, and admins checking their mods against it.
`42.21`	What it holdsThe previous Stable, from 28 September 2026. Steam labels it a temporary fall-back.	Who it suitsModded worlds waiting for their mods to be updated for 42.22.
`legacy41`	What it holdsBuild 41 (41.78.21).	Who it suitsGroups staying on Build 41 and its mods.

Steam also lists 42.19, which holds Build 42.19.2, a build from before Build 42 became Stable.

Which one to pick

Start on Stable. A new world with no mods, or with mods already updated for the current build, belongs here. The Indie Stone recommend it for the average player.

Use 42.21 while your mods catch up. When 42.22 became Stable, The Indie Stone noted that some mods may not work with the latest build, and that players who want to wait for mod authors can keep playing on 42.21. Steam calls the branch a temporary fall-back, so treat it as a stopgap: check each mod's Workshop page, and move the server to Stable once they have all been updated.

Use pre-release to look ahead. The Indie Stone aim it at modders, server admins and players happy to test, and ask you to copy any save you want to come back to first: a save from pre-release may not work in the final release. It suits a spare test world better than the one your group cares about.

Use legacy41 for Build 41. Build 41 saves are not compatible with Build 42, in The Indie Stone's own words, so a Build 41 world stays on legacy41 and a move to Build 42 means a new world.

Set the branch on the server

On your own PC, stop the server and run the SteamCMD install again with the branch name after -beta:

steamcmd +force_install_dir ~/pzserver +login anonymous +app_update 380870 -beta 42.21 validate +quit

Swap 42.21 for pre-release or legacy41, or for public to go back to Stable. The rest of the setup is in the guide to hosting a Project Zomboid server.

On our servers, a new server follows Stable. To change it, open Settings → Game version, type the branch name in the Steam branch box (public, pre-release, 42.21 or legacy41) and press Change version. The panel stops the server and reinstalls the game on that branch, and the world stays where it is. From then on the server updates within its branch each time it starts (Update on start, in All settings → Startup settings, on by default).

Set the same branch for every player

In the Steam Library, right-click Project Zomboid, choose Properties, then Game Versions & Betas, and pick the same branch as the server. Steam downloads that build.

A player on another branch is turned away with “Server version (…) does not match the client (…).” The other join errors are in Project Zomboid server not showing, or friends can't join.

What happens to your world when you switch

Forward, to a newer build. The game converts the save for the new version. In single player it asks first and keeps the old save beside it with _backup added to the name. A dedicated server's settings file has BackupsOnVersionChange=true by default. Take your own copy all the same.
Back, to an older build. A world saved on a newer build may not load on an older one. Take a copy before you switch, so you can return to it.
Between Build 41 and Build 42. Plan on a new world, as above.
Modded worlds. The Indie Stone say they can't give technical support for modded saves, so your own copy matters most here.

Keep your own copy: download your files from the panel's Files page, as one .zip or over SFTP.

A safe order for switching

Agree the branch with your group, so everyone changes on the same day.
Stop the server and download the world.
Change the branch on the server and let the install finish.
Each player picks the same branch in Steam and waits for the download.
Start the server, join, and check the world and its mods before the whole group piles in.

Want a server that follows the branch you choose and updates itself at every start? See our Project Zomboid servers.

Branches and builds as Steam listed them on 12 November 2026.