Project Zomboid Build 42 Dedicated Server: A Practical Setup Checklist

Build 42 is now the version most Project Zomboid groups play. The Indie Stone moved 42.20 to the public Stable branch in July 2026 with multiplayer included, and 42.21 followed in September with fixes for zombies duplicating in multiplayer. If you are setting up a dedicated server for your group right now, here is a checklist of the things that actually cause trouble, in the order you will run into them.

1. Pick a branch and make everyone match it

The server and every player have to be on the same branch. That sounds obvious, but it is the number one reason friends "can't connect".

• Build 42 (Stable): the default for new worlds.
• Build 41 (legacy41 beta branch): still exists for groups with a long-running world. Build 41 saves do not carry over to Build 42, so if your group has a 200-day B41 save, either stay on legacy41 or accept a fresh start.

Decide this before anyone builds a base. Switching later means a new world.

2. Know the four config files

A dedicated server keeps its configuration in four files named after the server. With the default name servertest you get:

• servertest.ini – server options (name, password, ports, mods, backups)
• servertest_SandboxVars.lua – the sandbox rules (zombie population, loot, day length, respawn)
• servertest_spawnpoints.lua and servertest_spawnregions.lua – where players spawn

If you rename the server with -servername, all four files follow that name. A classic mistake is editing servertest.ini while the server actually starts with a different name and reads a different file. When a setting "doesn't apply", check which file is in use first.

3. Lock the server down before you share the IP

A few servertest.ini options are worth setting on day one:

• Open=false turns the server into a whitelist. Admins then create accounts with the adduser command. For a friends-only server this beats a shared password that ends up in a Discord screenshot.
• PauseEmpty (on by default) stops game time while nobody is online. Keep it on for small groups so the world doesn't keep ageing while everyone is asleep.
• MaxPlayers defaults to 32. The server settings reference warns that higher counts can cause poor map streaming and desync, so don't raise it "just in case".

You can save the ini while the server is running and apply most changes with reloadoptions instead of a full restart.

4. Size RAM on players and mods, not on hope

The official PZ wiki sizes a server at a base of 3 GB plus about 500 MB per player. Its four-player example comes to 5 GB. Mods add to that, and big map mods add a lot.

Rough guide using that arithmetic:

Leave headroom on top if you run a long mod list. If you self-host, also remember to raise the Java heap the server is allowed to use (the -Xmx value in the server's launch config). Plenty of "laggy" servers have the RAM in the machine but not in the JVM.

5. Load Workshop mods with both lines

Workshop mods load through two lines in servertest.ini, and a modded server needs both:

• WorkshopItems= takes Workshop IDs (the number at the end of each mod's Workshop URL), separated by semicolons. This tells the server what to download.
• Mods= takes mod IDs (the id= value inside each mod's mod.info). This decides what actually loads.

One Workshop item can contain several mods, so you may need more entries in Mods= than in WorkshopItems=. Map mods also need their folder name in the Map= line, otherwise the map simply isn't there.

Connecting players download the server's Workshop mods automatically, so you don't need to send everyone a mod list. What you do need to check is that each mod has a Build 42 version. Build 42 mods use common and version-numbered folders that Build 41 mods lack; an old B41-only mod is a common reason a B42 server refuses to start or players get kicked on join.

Add mods a few at a time and restart between batches. When something breaks, you'll know which batch did it.

6. Turn on backups you never have to think about

Project Zomboid has built-in world backups, controlled from servertest.ini:

• BackupsCount – how many to keep
• BackupsOnStart – take one every time the server starts
• BackupsOnVersionChange – take one when the game updates

Turn on BackupsOnVersionChange at the very least. Game updates and mod updates are exactly when worlds get corrupted, and with Build 42 still moving quickly you will see updates. Before you add or remove a mod manually, take a copy of the save folder too.

Also shut the server down cleanly (save, then quit) rather than killing the process. A hard kill mid-save is the easiest way to lose a few hours of progress.

7. Open the right ports and choose a sensible location

By default the game uses UDP ports 16261 and 16262. If you host at home, forward both over UDP, not TCP. Players connect via Join → Favorites using the server's IP and port 16261.

Location matters more than people expect. Zombie hordes and vehicle driving feel noticeably worse at high ping, so put the server close to the majority of your players. For a European group, a data centre in Frankfurt or Amsterdam usually keeps everyone in a comfortable range; for a group spread from Spain to Sweden, pick something central.

8. Self-host or rent?

Self-hosting is great if you have a spare machine that can stay on, a decent upload speed and you don't mind port forwarding and updating things yourself. If you'd rather not keep a PC running all night, a rented server saves the hassle. For reference, GGameHost's Project Zomboid servers start at $10.99/mo for 4 GB RAM (fine for a duo by the wiki maths), with 6 GB and 8 GB plans for bigger groups, seven European locations and a one-click mod installer.

Whichever you choose, the checklist is the same: match the branch, edit the right file, whitelist, size RAM honestly, use both mod lines, and keep backups on. Do that and your group's biggest problem will be the zombies, not the server.