Project Zomboid Build 42 dedicated server: setup guide

A Project Zomboid Build 42 dedicated server keeps your group's Knox County run going even when nobody has the game open. Since 29 July 2026, Build 42 is the stable version, multiplayer included. This guide covers what changed for servers, how to host one free on your PC or 24/7 with us, and how to configure it.

If you would rather skip the install, our Project Zomboid server hosting always installs the latest stable Steam build. If you come from another survival game, the structure matches our Valheim dedicated server guide.

• Version: Build 42 has been Steam's public stable branch since 42.20. The current one is 42.21, released to stable on 28 September 2026.
• Build 41 is still available, but only on the legacy41 beta, and its saves do not work on Build 42.
• Ports: the server uses 16261/UDP and 16262/UDP.
• Free: you can host it yourself with Steam's free server tool. On 1up, Project Zomboid needs at least 3 GB of RAM: it runs on Free with the hourglass at ×2, and 24/7 from Starter.

1. Build 42 and multiplayer: what changed

Build 42 multiplayer reached the Unstable branch on 11 December 2025 with 42.13, as work in progress. The Indie Stone then advised whitelisted servers and no more than 20 players.

On 29 July 2026, 42.20 went straight to the public stable branch. Since that day, anyone who downloads the game or the server without picking a beta gets Build 42. What matters to an admin:

• Build 41 saves do not work on Build 42. Anyone who wants to stay on 41 has the legacy41 beta, according to the launch checklist.
• More players. Hotfix 42.20.3 improved the server player limit, with support for up to 254 players and admin access when the server is full, and fixed a memory leak that degraded servers over time.
• Patch cycle. With 42.21, every update goes to Unstable first, the community tests it, and then it reaches stable.
• Server fixes in 42.21. According to the 42.21 notes: less zombie duplication in multiplayer, a notice when a player connects with a different game version, and a fix for players entering dedicated servers without proper Steam authentication, which had prevented SteamID bans.
• Mods. 42.20.4 disabled the Lua methods loadstring and loadstream for security, and 42.21 re-enabled them. Some mods that broke in August should work again.

The practical rule: the server and every player must be on the same version. If someone is on Unstable or legacy41, they will not get into a server on the stable branch.

2. Host it free on your PC

The PZwiki, the wiki The Indie Stone links from its patch notes, describes two ways to install the server, both free:

• From Steam: filter your library by Tools and install Project Zomboid Dedicated Server. Do not launch it through Steam.
• With SteamCMD: log in anonymously and download app 380870:

force_install_dir C:\PZServer
login anonymous
app_update 380870 validate
quit

To stay on Build 41, the same page gives app_update 380870 -beta legacy41 validate.

Then:

1. Forward 16261/UDP and 16262/UDP on your router to your PC.
2. Edit StartServer64.bat and change -Xms and -Xmx. The wiki warns that the file asks for 16 GB by default and the server fails to start if your PC does not have it.
3. Run it. On the first start it asks for the password of the admin account.
4. The configuration lives in Zomboid\Server\servertest.ini under your user folder, and the world in Zomboid\Saves\Multiplayer\servertest.

It is free, but the server only exists while your PC is on, and Build 42 wants a fair amount of memory. It is the ideal way to try it with two or three friends.

3. Create a Project Zomboid server on 1up

1. Create an account and press Create server.
2. Pick Project Zomboid. On Free it runs with the hourglass at ×2 (your free time drains twice as fast); Starter and up keep it online 24/7.
3. Pick a region, London or Paris. The wizard measures your ping and suggests the closest.
4. In the settings step, choose the slots, PvP and, if only the accounts you create should join, Whitelist on (section 5). Tick Protect with a password if you like. You can change PvP and the whitelist later in the Game tab.
5. Create the server. The first start downloads the game from Steam and generates the world, so it takes a few minutes.
6. Once it is online, the Overview shows the IP line with the address and port your friends need.

Our server downloads the game at every start when a new build is out on Steam's stable branch. We do not bake the game files into our image because The Indie Stone's EULA forbids it. So a restart after a patch updates the server; tell your players to update too.

4. The panel settings

The Game tab groups the servertest.ini settings we manage. All of them apply on restart.

The rest of servertest.ini and the servertest_SandboxVars.lua file, with the game rules, are edited in Files, in the Zomboid/Server folder. Take a backup first and restart afterwards. The keys the panel manages, such as the ports, PVP or Open, are rewritten at every start, so change them in the Game tab.

5. How your friends join

Our servers do not announce themselves in the game's public browser (Public=false), so your friends join by IP. According to the wiki, on Build 42:

1. They open Project Zomboid and press Join.
2. In the Favorites tab, they add a server.
3. They type the IP and port from the IP line of the Overview. On our nodes the port is not 16261, so copy both numbers from the panel.
4. They choose an account name and password. The account is created on the server the first time they join, so they must remember that password.
5. If you set a Server password, they type it too. Then they save and join.

About the whitelist: with Whitelist on, in the wizard or in the Game tab, the server starts with Open=false and, as the server settings wiki page explains, only accounts an administrator creates can join. Create each one in the panel Console with adduser, the player's name and the password they will type; only you and your co-owners can run it, and the panel never shows that password again. removeuserfromwhitelist takes an account off the list. For a casual group of friends, the server password is simpler.

If you want players beyond your group, switch on Show on the public list in the Server tab, Address and ports section: your server then appears on our public server list with its IP. Our upcoming guide to public Minecraft Java servers covers the list in detail, and it works the same way for Project Zomboid.

6. Make yourself admin and moderate

The shortest path: join the server with your own account and, in the panel Console, run setaccesslevel with your name and the admin level. From then on you can use admin commands from the game chat, with a slash in front.

The console accepts the commands from the admin commands list that we reviewed, among them:

• servermsg "message" to warn everyone, for example before a restart.
• kickuser and banuser, with an optional -r "reason"; unbanuser lifts a ban.
• setaccesslevel with levels such as admin, moderator, gm, observer or none.
• players to see who is online and save to save the world.

The console's quick commands are servermsg, kickuser, banuser, players and save. Granting or removing admin stays with the owner and the co-owner of the server on 1up; a panel moderator cannot.

The panel's Admin password belongs to the admin account the server creates on its first start. For your personal account, use setaccesslevel.

7. Workshop mods

Mods are included from Starter, the first paid plan with enough memory for Project Zomboid. To add them:

1. Copy the number from each Workshop item's URL and paste it into Workshop (ids separated by ;).
2. Add each mod's id to Mods (ids separated by ;). The wiki says it is in the mod's info.txt file, and many authors copy it onto their Workshop page. One item can carry several.
3. Restart. The server downloads the mods at start and, according to the wiki, players download them when they connect.

The Indie Stone asks players to reproduce bugs without mods before reporting them, and some mods take a while to catch up with each Build 42 patch. Add them one at a time and take a backup first.

8. RAM, slots and backups

Project Zomboid needs 3 GB to start on 1up, and we recommend 6 GB for a large or modded group. Java gets three quarters of the plan's RAM. From our pricing page:

Take a backup in the Backups tab before every patch and before adding mods. If you are torn between paying and hosting it yourself, our comparison of free vs paid game server hosting helps you decide.

Tested on Project Zomboid Build 42.21 (dedicated server public-branch build 25485538), 2026-10-07: settings, files and the way to connect checked against our image in 1up v0.268.0. A production server on 42.21 started and answered Steam on its public port; we have not yet documented a full game client session on our cluster.

Change log

• 2026-10-07: first version, on Build 42.21 stable.
• 2026-10-20: Free now runs Project Zomboid with the hourglass at ×2; Studio is €25.
• 2026-10-26: current plan table: Starter €5/4 GB, Pro €10/8 GB/60 GB/30 slots, Studio €20/16 GB/80 GB/50 slots/10 backups.