Project Zomboid multiplayer: set up a server for friends

Project Zomboid is a game about surviving a long time, which makes a server that disappears when the host logs off feel wrong. A dedicated server keeps Knox Country alive between sessions: your safehouse stays stocked, the generator keeps running down, and whoever logs in Tuesday finds the world exactly where Sunday left it. Here’s the full setup on Windows.

Install the server and set the admin password#

1. Install Project Zomboid Dedicated Server

   In Steam, filter your library by Tools, find Project Zomboid Dedicated Server, install it. Then Manage → Browse local files to open the folder.

2. Run StartServer64.bat

   Double-click StartServer64.bat. The first run asks you to enter a new admin password in the console window, twice. Type it (you won’t see characters), press Enter. That’s your in-game admin login; the username is admin.

3. Wait for it to generate

   The console prints a lot, then *** SERVER STARTED ***. Close it cleanly with quit typed into the console. Now you have a config to edit.

Edit servertest.ini#

The server wrote its config to your user folder, not the install folder:

C:\Users\<you>\Zomboid\Server\servertest.ini

Open it in Notepad. The file is long; these are the lines that matter for a friend group:

PublicName=Knox County Night Shift
Public=false
Password=meaty-bits-7
MaxPlayers=16
PVP=false
PauseEmpty=true
Open=true
SaveWorldEveryMinutes=10

• Public=false keeps it off the browser; friends join by IP. Set true and add a PublicDescription if you want it listed with a password.
• PauseEmpty=true freezes time when nobody’s on, so the zombies don’t migrate and the food doesn’t rot while you’re at work. Most groups want this.
• PVP=false is the sane default for co-op. Safehouses and faction settings live further down if you want claims.

Sandbox options (loot rarity, zombie count, XP multipliers) are in servertest_SandboxVars.lua next to it. Easier way: set them once from inside the game’s Host screen, then copy the values over.

Open the ports#

Project Zomboid uses UDP 16261 for the game and UDP 16262 for the direct player connection. On the current build those two are enough.

1. Reserve your PC's local address

   In your router’s DHCP settings, pin your PC’s IP so the forwarding rule survives a reboot.

2. Forward UDP 16261 to 16262

   Add a rule for UDP 16261-16262 pointing at your PC. Then confirm Windows Firewall allowed java.exe (the server runs on Java); if it didn’t ask, add the inbound rule manually.

Give the server enough memory#

The server is a Java app and its memory is fixed at launch by the -Xmx flag in the start script. Open StartServer64.bat and look at the ProjectZomboid64 line. For a vanilla map and up to 8 players, 4 to 6 GB is comfortable:

-Xms4g -Xmx6g

Heavy map mods, a lot of players, or long uptime want 8 GB or more. If the console starts printing memory warnings or the server stutters every few seconds, this is the number to raise.

Add mods (the part everyone eventually does)#

Zomboid without mods is rare. In servertest.ini, two lines control it:

WorkshopItems=2392709985;2503622437
Mods=tsarslib;BetterSortCC

WorkshopItems are the numbers from each mod’s Steam Workshop URL. Mods are the mod IDs from inside each mod’s page or its mod.info. Order matters for dependencies; the library mod goes first. Players who join download the mods automatically and are prompted to enable them.

Get your friends in#

In Project Zomboid: Join → Favorites → Add. Enter your public IP, port 16261, a display name, and the server password. Save it as a favorite. The first join downloads mods and takes a minute; after that it’s instant.

You connect from the same network with the local IP. The admin account and password you set on first run give you the admin panel in game (ESC → Admin), where you can teleport, spawn items and kick the friend who keeps opening doors during the helicopter.

Keeping it alive#

Restart the server when Steam updates the game, back up Zomboid\Saves\Multiplayer on a schedule, and don’t let Windows sleep. The server also writes a log with every restart in Zomboid\Logs; when something breaks, that’s where the answer is.

If you’d rather spend those hours in the world than around it, a rented server gives you the same servertest.ini, the same mods, and none of the port forwarding.