How to Make a Project Zomboid Server (Build 42, 2026 Guide)

A Project Zomboid dedicated server keeps Knox County running for your group whether the original host is online or not. Build 42 multiplayer became the stable default on 29 July 2026, bringing server authoritative inventories and loot, and it changes a few things for server owners. This guide walks through a full self hosted setup on Windows or Linux, and ends with a quicker option if you would rather skip it.

Short on time? A hosted Project Zomboid server is online in about 60 seconds, with no SteamCMD, Java settings or ports to deal with. Our quick start guide shows every step.

What you need

• A PC or server that stays on. The dedicated server runs on Windows and Linux. Knox County only moves forward while the server runs, so if the host's PC goes to sleep, so does your world. That is the main reason groups move to a hosted server.
• More RAM than you might expect. Build 42 is noticeably hungrier than Build 41, and every mod and map adds to it:

• A modern CPU with good single core speed.
• Around 10 GB of disk space, plus room for Workshop mods and a growing world.
• Access to your router to forward UDP ports.

See how much RAM a game server needs for more on sizing.

Step 1: Install SteamCMD

Download SteamCMD from Valve. On Windows, extract it to a folder like C:\steamcmd and run it once. On Linux, install the steamcmd package or the tarball, and create a normal user to run the server rather than root.

Step 2: Download the dedicated server

The Project Zomboid dedicated server is Steam app ID 380870, separate from the game itself, and downloads anonymously. Build 42 is the default branch, so no beta flag is needed.

Windows:

steamcmd +force_install_dir "C:\pzserver" +login anonymous +app_update 380870 validate +quit

Linux:

./steamcmd.sh +force_install_dir /home/pzuser/pzserver +login anonymous +app_update 380870 validate +quit

Run the same command after every game update, because players on a newer build cannot join an older server. If your group wants to keep playing a Build 41 world, install the legacy branch instead by adding -beta legacy41 after app_update 380870. Build 41 saves do not load in Build 42.

Step 3: Set the RAM

The server is a Java program, and its memory limit is set in ProjectZomboid64.json in the install folder. Find the vmArgs list and change the -Xmx value, for example to give the server 8 GB:

"-Xmx8g"

If there is also an -Xms line, set it to the same value. Too little memory causes stutters and out of memory crashes. Too much starves the operating system, so leave a few GB free.

Step 4: First start and admin password

Start the server with StartServer64.bat on Windows or ./start-server.sh on Linux. The very first launch asks you to create a password for the built in admin account. Type it twice and the server continues starting. When the console reports that the server has started, it is ready.

This first start also creates the config files in your user profile:

• Windows: C:\Users\<you>\Zomboid\Server\
• Linux: ~/Zomboid/Server/

The world itself is saved under Zomboid/Saves/Multiplayer/.

Step 5: Edit servertest.ini

servertest.ini holds the server settings. Stop the server before editing it, because the server rewrites the file when it shuts down and your changes will vanish otherwise. The settings most people change:

• PublicName and PublicDescription: how the server appears in the browser.
• Public: true to list it in the public browser, false for a private server.
• Password: a join password. Leave it empty for an open server.
• MaxPlayers: the player limit. More players need more RAM.
• PVP: true or false.
• DefaultPort: 16261 by default.
• Open: when true, anyone can create an account by joining. Set it to false for a whitelist only server.
• WorkshopItems and Mods: covered below.

The name servertest is the default server name. To run a differently named world, start the server with -servername myworld and it uses myworld.ini instead.

Step 6: Sandbox settings

servertest_SandboxVars.lua in the same folder controls the gameplay: zombie population and speed, loot rarity, when water and electricity shut off, how fast time passes and more. Edit it with the server stopped. Most sandbox changes only apply fully to a new world, and some, such as zombie counts, only affect newly loaded areas.

Step 7: Add Workshop mods

Two lines in servertest.ini control mods, and both take a semicolon separated list:

• WorkshopItems= the numeric Steam Workshop IDs, from the end of each mod's Workshop URL. The server downloads these on start.
• Mods= the Mod IDs, which switch the mods on. You find the Mod ID on the mod's Workshop page or inside its files. Copy it exactly.

Map mods also need their map folder name added to the start of the Map= line, before the base map. Only use mods that support Build 42 on a Build 42 server. Players download the same mods automatically when they join.

Step 8: Open the ports

Project Zomboid uses UDP, not TCP. Forward these to your server's local IP:

Allow Java or the server through Windows Defender Firewall or ufw too. A TCP forward on these ports looks correct in the router but does nothing. Our port forwarding guide covers the process and testing. If your ISP uses CGNAT or you cannot change router settings, a hosted server avoids this step entirely, because it has its own public address.

Step 9: Let friends connect

1. Launch Project Zomboid on the same build as the server.
2. Click Join on the main menu.
3. Enter your public IP, port 16261, the server password if there is one, and a username and password for their account on the server.
4. Click Save, then select the server and click Join.

The first time a player joins an open server, their username and password become their account, so they should reuse the same ones next time. Everyone needs their own copy of the game.

Common problems

• Stuck on "Connecting" or timing out: the ports are forwarded as TCP instead of UDP, or the firewall is blocking the server. See Project Zomboid can't connect to server for every other cause.
• Mod errors on join: a mod in Mods= has no matching entry in WorkshopItems=, a Mod ID is misspelled, or a mod does not support Build 42.
• "Workshop item version is different than server's": a mod updated after the server started. Restart the server. Details in our Workshop error fix.
• Config changes disappear: the file was edited while the server was running. Stop it first.
• "Server version is different": the server or the player is on another build. Update the server with SteamCMD, or check nobody is on the legacy41 branch by accident.
• Stutters and crashes as the world grows: -Xmx is too low. Raise it, within what the machine has free.
• Bases rolled back after a crash: always stop the server with the quit command so it saves. Killing the process can lose progress.

The easy way

Hosting Project Zomboid yourself teaches you a lot, but the upkeep adds up: a PC running around the clock so the world keeps going, Java memory tuning as Build 42 grows, ini files that reset if you edit them with the server running, UDP ports on your home network, and restarts every time a Workshop mod updates.

A GamezServers Project Zomboid server handles the hosting side. Pick a plan from 6 GB, pay, and your server is live in about 60 seconds with its own address, servertest.ini and the sandbox file editable in the browser, a full console for setaccesslevel, and one click backups before mod updates. Split the bill with up to 9 friends, and new customers get 50% off the first month. The Project Zomboid quick start guide walks through it.