How to Set Up a Project Zomboid Build 42 Multiplayer Server

Build 42 multiplayer is here. After years of singleplayer-only development, The Indie Stone released multiplayer support for Build 42 in December 2025, and it has been receiving steady patches since. The update brings overhauled crafting, animals, basements, new game modes, and a lot of under-the-hood improvements to how servers run.

If you have been waiting for Build 42 MP to set up a server with friends, this guide walks through both hosted and self-hosted options, RAM requirements, the settings that matter, and what is new in Build 42 that affects how you run a server.

What You Need to Know Before Starting

RAM Requirements

Build 42 is hungrier than Build 41. The new crafting systems, animals, and world simulation all add overhead. Here is what to plan for:

These numbers are higher than most guides for Build 41. That is expected - Build 42 is a much larger game now. RAM usage also grows over time as players explore more of the map and the world accumulates state. A server that starts at 6GB usage on day one can climb to 10GB+ after a week of active play.

Version Matching

Everyone needs to be on the same version - server and clients. Since Unstable updates frequently (sometimes multiple times per week), pick an update day with your group and stick to it. If one person updates and the server hasn’t, they cannot connect until the server catches up.

Option A: Using a Hosting Provider

If you want to skip setting up SteamCMD, port forwarding, and keeping a machine running 24/7, a hosted server gets you into Build 42 MP in a few minutes.

Setting Up on WinterNode

1. Order a Project Zomboid server from the game page - select at least 8GB of RAM for Build 42
2. Once provisioned, go to Server Options in your control panel
3. Set the Game Branch to the Build 42 Unstable branch (see our beta branches guide for the exact steps)
4. Set your Server Name and admin credentials in Server Options
5. Start the server and let it generate the world - first boot takes a few minutes

That is it. Your server gets an IP and port you can share directly. No router configuration, no firewall rules, no SteamCMD.

What you get with WinterNode:

• One-click Build 42 branch switching through the control panel
• Automatic backups every 12 hours with 45-day retention
• File manager and SFTP access for config editing and world management
• No CPU limits - PZ can burst when it needs to
• Unmetered storage for worlds that grow over time

All game servers run $1.99/GB of RAM. An 8GB Build 42 server comes to $15.92/mo, and a 12GB server for a larger group is $23.88/mo. No hidden fees for CPU, storage, or support.

Get your Project Zomboid server →

Connecting

Once your server is running, players connect through the in-game Join menu. Use the Favorites tab and enter the server IP and port from your control panel. For the full walkthrough with screenshots, see our connecting guide.

Option B: Self-Hosting

Running PZ on your own hardware is free, but comes with real tradeoffs - especially for Build 42 where RAM requirements are higher and the Unstable branch means more frequent updates.

Installing the Server

You need SteamCMD. Download it from Valve’s developer wiki and install it for your platform.

Then pull the server files with the Unstable beta branch:

steamcmd +login anonymous +force_install_dir /path/to/pz-server +app_update 380870 -beta unstable validate +quit

App ID 380870 is the Project Zomboid Dedicated Server. The -beta unstable flag is required for Build 42 - without it you get Build 41.

First Launch

On Linux:

cd /path/to/pz-server
chmod +x start-server.sh
./start-server.sh

On Windows, run StartServer64.bat from the server directory.

The first launch generates config files and a world. It will ask you to set an admin password through the console. Pick something your group will remember - this is the password for the in-game admin panel, not the server join password.

Server config files land in:

• Linux: ~/Zomboid/Server/
• Windows: %USERPROFILE%\Zomboid\Server\

You will find two key files here: servertest.ini (server settings) and servertest_SandboxVars.lua (world/gameplay settings). The “servertest” part is the default server name - it changes if you rename your server.

Port Forwarding

PZ uses UDP port 16261 by default, plus one additional UDP port (16262) for Steam integration. Forward both on your router to the machine running the server.

The usual process:

1. Find your server machine’s local IP (ipconfig on Windows, ip addr on Linux)
2. Log into your router admin panel
3. Forward UDP ports 16261-16262 to that local IP
4. Add firewall exceptions for those ports on the server machine

Players connect using your public IP and port 16261. You can find your public IP at whatismyip.com.

Self-Hosting vs. Hosted: Honest Comparison

Self-hosting works well if you have a spare machine with 16GB+ RAM and enjoy server administration. For most groups that just want to play together without one person being the designated IT department, hosted is the lower-friction option.

Key Server Settings for Build 42

Game Modes

Build 42 replaced the old preset system with four distinct game modes:

• Apocalypse - The “canon” mode. Balanced difficulty with deadly combat that punishes mistakes. This is the default and what most groups should start with.
• Rising - A more relaxed experience focused on building and base management. Fewer combat pressures, more resources. Good for groups that want to focus on the new crafting and animal systems.
• Outbreak - Faster-paced with more action and less emphasis on the survival crafting loop.
• Extinction - Hardcore mode with sprinters, scarce supplies, and punishing difficulty. Not recommended for a first Build 42 playthrough.

Each mode has a corresponding preset in Custom Sandbox if you want to use one as a starting point and tweak individual settings.

To set the game mode on your server, you can either configure it through the admin panel in-game or edit the SandboxVars.lua file directly. On WinterNode, you can edit this file through the File Manager or SFTP.

Zombie Settings

The zombie configuration in SandboxVars.lua under the ZombieLore section controls population, speed, strength, and behavior. Key settings to consider:

• Population - How many zombies spawn. Higher player counts can handle higher populations, but Build 42’s other systems already add server load. Start at Normal and adjust.
• Speed - Shamblers (default for Apocalypse) vs. sprinters (Extinction). Sprinters are significantly harder and add more server processing per zombie.
• Respawn - Whether zombies respawn in cleared areas and how quickly. Turning this off makes the world progressively easier over time. Turning it on keeps things dangerous but means cleared zones do not stay safe.

Build 42-Specific Settings

Build 42 introduces sandbox options for its new systems:

• Animals - Control spawn rates and types. Animals add a long-term food source but also server overhead. If your server is struggling with performance, reducing animal spawns is one lever to pull.
• Crafting stations - The new tiered crafting system (stone age furnaces through electrical machines) is controlled by loot distribution and crafting skill progression. These settings live in the sandbox options.
• Basements - Randomly generated in buildings. These are baked into world generation, so you cannot toggle them after the world is created.

Server INI Settings Worth Checking

In your servertest.ini (or whatever your server name is), a few settings are especially relevant for multiplayer:

# Maximum number of players
MaxPlayers=16

# Server visibility
Open=true
Public=false

# PvP toggle
PVP=false

# Sleep settings - important for multiplayer
SleepAllowed=false
SleepNeeded=false

# Voice chat
VoiceEnable=true

For private groups, set Open=true (allows connections) but Public=false (hides from server browser). Use a whitelist for access control - see our PZ quick start guide for whitelist setup.

Sleep is disabled by default in multiplayer for good reason - one player sleeping would fast-forward time for everyone. Leave it off unless your group has a specific plan for handling it.

Inviting Friends

Once the server is running:

1. Share the server IP and port with your group
2. Everyone opens Project Zomboid, clicks Join, then uses the Favorites tab
3. Enter the IP in “Address” and port in “Port”
4. If you set up a whitelist, players need the username and password you assigned them
5. If the server is open (no whitelist), players choose their own username and password on first connect - these become their login credentials going forward

Make sure everyone is on the same Build 42 Unstable version before connecting. A version mismatch will show a connection error with no useful message.

Build 42 Tips for Server Operators

Start fresh. Build 41 worlds are not compatible with Build 42. Do not try to migrate them - start a new world.

Disable mods initially. Many Build 41 mods are not updated for Build 42 yet. Start vanilla, verify the server is stable, then add mods one at a time. Check each mod’s Steam Workshop page for explicit Build 42 compatibility.

Monitor RAM usage. Build 42 servers can see memory grow substantially over multi-day sessions as players explore. Watch for signs of memory pressure (server lag spikes, long save times) and restart the server periodically if needed.

Keep backups. Unstable branch updates can break saves. Before updating the server, back up your Zomboid/Server/ and Zomboid/Saves/ directories. On WinterNode, automatic backups handle this for you with 45-day retention - you can roll back if an update causes problems.

Admin setup matters. Grant admin to at least one trusted player. The in-game admin panel gives you control over the sandbox settings, player management, and server state without needing to touch config files. Our quick start guide covers whitelist setup, admin commands, and spawn rate configuration.

Build 42 multiplayer is the version of PZ that a lot of people have been waiting for. The new crafting, animals, and survival loop are significantly deeper than Build 41, and experiencing that with friends makes it better. Yes, the Unstable branch means occasional bumps - but most groups find it well worth it.

If you want to get a server running without the self-hosting overhead, WinterNode has one-click PZ setup with Build 42 branch switching built into the panel. $1.99/GB, no CPU limits, and support from people who actually play these games. Get your Project Zomboid server →

Questions? Open a ticket or hop into our Discord. We are happy to help with Build 42 server setup.