If you want to try Build 42 multiplayer, the first step is moving your server onto the correct beta branch. For anyone setting up a Project Zomboid build 42 server, that usually means switching to the Unstable branch, which the official Project Zomboid team identifies as the current access point for Build 42 on Steam.
Before making the switch, it is worth preparing properly. Build 42 is not just a small patch over Build 41. It introduces major changes, and official notes warn that older saves are not compatible in some cases, while unstable multiplayer updates may also disrupt ongoing server progress. That is why changing branches should be treated more like a fresh server transition than a normal update.
Why You Should Back Up First
If you already have a world running on another branch, especially Build 41, back it up before changing anything. This matters most if you want the option to return to your old world later without losing player progress, server settings, or other important files.
The reason for this is simple: Build 42 multiplayer is still being actively developed, and official guidance notes that older saves can become incompatible. In practical terms, that means switching branches without backing up first can leave you with a world you cannot safely restore later.
A backup gives you a safety net. You can test Build 42, start fresh if needed, and still keep your old branch data available if you decide to roll back.
How To Switch Branches When Self-Hosting
If you are self-hosting your Project Zomboid server, switching to Build 42 usually means updating the Project Zomboid server through SteamCMD, which is Valve’s command-line tool for installing and updating dedicated servers.
For Build 42, the branch you want is:
unstable
Step 1: Install SteamCMD
Before you can switch branches, you need SteamCMD installed on the machine where your server will run. SteamCMD is the tool used to download and update the Project Zomboid dedicated server files.
Step 2: Open SteamCMD
Launch SteamCMD on your server machine.
On Windows, this is usually steamcmd.exe.
On Linux, this is usually ./steamcmd.sh.
Once SteamCMD opens, you will see a command prompt where you can enter install and update commands.
Step 3: Log In
Inside SteamCMD, enter:
login anonymous
This logs you into SteamCMD so you can download the dedicated server files.
Step 4: Set Your Server Install Folder
Next, tell SteamCMD where your Project Zomboid server files should be installed.
For example, on Windows:
force_install_dir C:\PZServer
On Linux, it could look like this:
force_install_dir /home/youruser/pzserver
This sets the folder where the dedicated server files will be placed.
Step 5: Install Or Update The Build 42 Branch
Now enter:
app_update 380870 -beta unstable validate
This command does three things:
app_update 380870installs or updates the Project Zomboid dedicated server-beta unstabletells SteamCMD to use the Build 42 branchvalidatechecks the files after download to make sure the install is complete
Step 6: Wait For The Download To Finish
SteamCMD will now download or update the server files into the folder you selected. Do not close the window while this process is running.
Once it finishes, your server files should now be on the Build 42 branch.
Step 7: Start With A Clean Server If You Are Moving From Build 41
If you are switching from Build 41 to Build 42, it is safest to start with a clean server file set. The branches do not use the same save path cleanly, and older files may cause problems if they are left in place.
Before making the switch, back up your existing saves and config files. Then either use a clean server folder or remove the old server files before launching Build 42.
Step 8: Make Sure Players Are On The Same Branch
After updating the server, anyone joining also needs to be using the same branch. If your server is on unstable but players are still on the default branch, they may not be able to connect correctly.
Example SteamCMD Setup
Here is the full process in one block:
login anonymous
force_install_dir C:\PZServer
app_update 380870 -beta unstable validate
quit
The most important part here is not treating the branch switch like a normal hotfix. Because Build 42 multiplayer can involve save incompatibilities and structural differences from older versions, reusing existing files without caution can cause problems.
How To Switch To Build 42 With Pine Hosting
If you are using Pine Hosting, the process is much easier because you do not need to manually run SteamCMD commands or handle the reinstall from the command line. For players looking into Project Zomboid build 42 server hosting, this makes the branch change much simpler to manage.
First, go to the Startup tab in your Pine Hosting panel.
Find the Steam Beta Branch field and enter:
unstable
That matches the currently listed Build 42 access branch used for Steam beta participation.
After that, go to the Settings tab and click Reinstall Server.
When reinstalling, choose to clear all server files. This is the safest option because Build 42 and older branches do not share the same progression path cleanly, and official notes warn about save incompatibility across versions. Clearing the files helps avoid conflicts between old branch data and the new server install.
Once the reinstall is done, start the server and test it using a client also set to the same Build 42 branch.
Video: How to Change the Server Branch in Project Zomboid Build 42 Multiplayer Dedicated Server Guide
Why A Clean Reinstall Matters
When moving from Build 41 to Build 42, keeping old server files in place can create avoidable issues. The official Build 42 notes make clear that previous saves may not remain compatible, which is why using a clean reinstall is the safer route when changing branches.
That does not always mean your old data is useless. It just means it should be preserved separately rather than dropped into a different major branch and expected to work normally. If you want to keep older progress, save it as a backup first and then let the new Build 42 install start from a clean file set.
What To Do If You Want To Keep Your Build 41 Progress
If you have an active Build 41 world and do not want to lose it, make a backup before you switch branches. On Pine Hosting, that means going to the Backups tab and saving your server data before reinstalling.
This gives you a simple way to return to your previous branch later if you want to go back. Since Build 42 multiplayer is still evolving and unstable updates can affect ongoing saves, having that backup in place is the safest way to experiment without risking your original world.
Things To Keep In Mind Before Switching
Build 42 multiplayer is exciting, but it should still be approached carefully. The official release messaging describes it as unstable multiplayer access, which means testing, changes, and compatibility issues are all part of the experience.
That does not mean you should avoid it. It just means you should switch with realistic expectations. Back up your current branch, reinstall cleanly, and make sure everyone joining the server is on the same version.
If you are running a long-term community world and stability matters most, you may prefer to wait. If you want to experiment with the newest multiplayer changes, Build 42 can be a great test environment.
Host Your Project Zomboid Server With Pine Hosting
If you want a simpler way to manage branch changes, backups, reinstalls, and general server upkeep, Pine makes Project Zomboid server hosting much easier to handle. Instead of manually working through update commands and file cleanup, you can manage the important parts from one panel.
For anyone looking for more convenient Project Zomboid multiplayer server hosting, Pine Hosting gives you an easier way to switch branches, protect older progress with backups, and reinstall cleanly when major version changes require it. Whether you are testing Build 42 or planning a longer-term world, having straightforward tools in one place makes server management far less of a hassle.
