Project Zomboid Build 42: setting up a server with friends

Project Zomboid waited a long time for multiplayer in Build 42. The unstable branch got it in December 2025, and since 29 July 2026 version 42.20 has been on the stable branch — multiplayer included. The current stable version is 42.20.3 from 17 August. If you want a server with friends, you no longer need to pick a beta: the dedicated server (Steam app 380870) runs 42.20 by default. This article goes through what you need, which settings in servertest.ini and the sandbox matter, and where Build 42 differs from the Build 41 most players know.

What changed in Build 42

Build 42 is more than a version number. Crafting has been rebuilt around trades and workstations, there are animals you can keep and hunt, basements under buildings, new biomes and light that really falls through windows. For server admins the most important change is invisible: server management and the connection layer have been redone, with more stable connections and better handling of players logging in and out. The player maximum of a dedicated server is 254, far above what a group of friends will ever use.

The flip side of a big update: many Workshop mods have not yet been republished for stable 42.20. A mod list that worked a month ago can refuse to load after a patch. More on that below.

Servertest.ini: the settings to set right away

The file servertest.ini (the name comes from the default server name "servertest") holds the server settings that have nothing to do with the game rules. The most important:

• PublicName and PublicDescription: how the server appears in the list. Public=false keeps it out of the public list.
• Password: always set it for a group of friends.
• MaxPlayers: default 32; for a group of six set 8 or 10, which saves memory.
• PVP and SafetySystem: PvP off for co-op, or on with the safety system so players choose whether they can be attacked.
• PauseEmpty=true: the world stands still when nobody is online, so you do not come back to a rotten house with an empty fridge.
• SpawnPoint and SpawnItems: a shared starting place and optionally a starter kit for new players.
• DefaultPort (16261) and UDPPort (16262): must be open; on a hosted server the panel takes care of that.
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Sandbox: the rules of your world

The game rules — zombie density, food decay, electricity, loot, XP — live in a separate sandbox file (servertest_SandboxVars.lua) that you generate when creating the server or set through the panel. For a first server with friends these choices work well: zombie population normal with a peak after thirty days (so the first week is survivable), loot on Rare for food and weapons and Normal for tools, electricity and water shutting off between day 14 and 30 (so there is a real turning point), and XP multiplier 1.5 so whoever plays one evening a week does not fall endlessly behind. Do not set all the zombie lore options (memory, hearing, speed) to maximum; sneaky zombies with good memory are considerably more dangerous on a server with four players spread out than in single player.

Workshop mods without a broken world

You install mods with two lists in servertest.ini: WorkshopItems holds the numerical Workshop IDs from the Steam URL, Mods the mod IDs from each mod's mod.info file. Both must be correct, otherwise the server does not load or players load a different version than the server. With Build 42 one rule is added: check for every mod that it explicitly supports 42.x. A Build 41 mod almost certainly will not work and can block start-up. Add mods one at a time, start the server after each addition and back up the save folder before adding. How that works in our panel is in installing mods via the Steam Workshop.

After a game update the order is reversed: first wait until the mod authors have updated their mod, only then update the server. Anyone who updates automatically will find a server that does not start the morning after a patch.

Hardware: one fast core counts

Project Zomboid leans heavily on one processor core, especially for zombie AI and world simulation. More cores help little; a high clock speed does. For a group of four to eight players 4 to 6 GB of RAM is enough, and more players or large cities like Louisville call for 8 GB. NVMe storage makes a noticeable difference when loading chunks as players spread out. Our Project Zomboid servers therefore run on AMD hardware with NVMe and are online within a minute; the panel installs 42.20 by default.

Backups, resets and the death of a character

In Zomboid death is final: your character is gone, the world remains. That makes backups on a server different from other games: you do not want to "restore" a player, but you do want to be able to recover the world if a mod or a crash damages it. Daily backups of the save folder are enough; keep a few generations. If you want to start over after a few months, delete only the save folder and keep servertest.ini and the sandbox settings, so the new world has the same rules. Agree with the group when a reset happens; nothing is as demotivating as losing a base without notice.

Keeping an eye on performance

A Zomboid server gives little warning before it slows down. Watch the CPU usage of the one core doing the work in the panel: if it sits above 80 percent for long, it is time to lower the zombie population or let fewer players in at once. Memory grows with the number of loaded cells; players spread far apart each load their own part of the map. A group travelling together loads the server less than four soloists in four towns. Turn on PauseEmpty, because an empty server that keeps ticking costs power and only produces rot.

Step by step

1. Create the server (42.20 is the default), set a password, MaxPlayers to your group size plus two.
2. Set the sandbox: zombie population, loot, utility shut-off, XP. Save the file.
3. Back up the empty save folder, then add mods, one at a time.
4. Test with two players: log in, get through a night, log out and back in.
5. Automatic updates off, daily backups on, and invite the group.

In this order you have a server in one evening that survives the first weeks — and you know exactly where to look when an update or a mod spoils things.