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How to Install Mods on a Project Zomboid Server

Add Steam Workshop mods and map mods to your Project Zomboid server — Workshop IDs, Mod IDs, load order and fixes for common errors.

How to Install Mods on a Project Zomboid Server

A Project Zomboid server downloads Steam Workshop mods by itself: you tell it which Workshop items to fetch and which mods inside them to turn on, restart it, and every player who joins gets the same mods automatically. This guide shows where those settings live on a Lobby Maker server and how to avoid the mistakes that stop a modded server from starting.

Make a backup first (Backups tab). A broken mod list can stop the server from loading your world, and a backup takes seconds to restore.

1. Find the Workshop ID and the Mod ID

Every mod needs two values, and they are not the same thing:

  • Workshop ID — the number at the end of the mod's Steam Workshop address. In https://steamcommunity.com/sharedfiles/filedetails/?id=1234567890 it is 1234567890.
  • Mod ID — the mod's internal name. Authors list it at the bottom of the Workshop description as Mod ID: .... One Workshop item can contain several Mod IDs (a main mod and optional add-ons, for example) — enable only the ones you want.

Many mods also need other mods to work. They are listed under Required items on the Workshop page — add their IDs too.

Map mods also list a Map Folder on their Workshop page. Keep all three lists in a notepad; you will paste them in step 3.

2. Open your server's config file

  1. Open your server in the panel (My game servers → Server Panel).
  2. If the server has never been started, start it once and wait until it is up. The config file is created on the first start.
  3. Stop the server from the Console tab. Project Zomboid rewrites its config when it shuts down, so changes made while it runs can be lost.
  4. Go to the Files tab and open the .cache/Server/ folder.
  5. Open the .ini file named after your server — the Server Name from the Startup tab (for example MyServer.ini).
The Mods tab of your server has an Open config file button that takes you straight to this file.

3. Add the mods

Find these two lines and fill them in. Separate the entries with semicolons, without spaces:

WorkshopItems=1234567890;2345678901
Mods=\ExampleLibrary;\ExampleMod
  • WorkshopItems= takes the Workshop IDs — what the server downloads.
  • Mods= takes the Mod IDs — what the server turns on. Write every Mod ID with a backslash \ in front — that is the format of Build 42, which Lobby Maker servers run. Lists without the backslash still work on the current version.

Every Mod ID must belong to a Workshop item listed in WorkshopItems=. A mod that other mods depend on (a "library" or "framework") should come before them in Mods=.

Did you switch your server to Build 41 (legacy41 in Steam Beta Branch on the Startup tab)? Build 41 reads Mod IDs without the backslash: Mods=ExampleLibrary;ExampleMod. Build 41 mods don't work on Build 42 and the other way round.

Map mods

Map mods need one more line. Put the custom map folders first and keep the vanilla map last:

Map=ExampleMapFolder;Muldraugh, KY

Click Save Content, then Start the server from the Console tab.

4. Check that the mods loaded

The first start after adding mods takes longer: the server downloads every Workshop item before it loads the world. Watch the Console tab — you will see the Workshop items being downloaded, then the mods being loaded, and finally the line that the server has started.

Players don't need to subscribe to anything in advance: when they join, the game offers to download the server's mods. They only need to run the same game version as the server — the Steam Stable branch, unless you changed it.

Mods written in Java, such as the first-person mod Project Viewpoint, are the exception: every player has to install a Java loader on their own PC once. See How to install Project Viewpoint.

Common problems

"Workshop item version is different than server's" when joining. A mod was updated on the Workshop after your server downloaded it. Restart the server so it fetches the new version; players may need to restart their game as well.

A mod is listed in `WorkshopItems=` but does nothing. Its Mod ID is missing from Mods=, or it is misspelled — Mod IDs must match exactly, including capital letters.

The server crashes right after loading a mod. The mod is made for another game version: Build 41 and Build 42 mods are not interchangeable, and some mods only support certain 42.x updates. Check the Workshop page, remove the mod from both lines and start again.

The mods stopped working after a game update. Your server installs game updates on restart, and a mod that supports only the previous version stops loading until its author updates it. Check the mod's Workshop page or remove it until then.

My changes disappeared. The server was running while you edited the file and overwrote it when it stopped. Stop the server first, then edit.

Frequently asked questions

How many mods can a server run? There is no fixed limit, but every mod adds loading time and memory use. Big collections (50+ mods) need a plan with more RAM.

Can I add a whole Steam Workshop collection? Not in one go — add the Workshop IDs of the items in the collection to WorkshopItems= and their Mod IDs to Mods=.

Will adding mods reset my world? No, your save stays. Removing a mod that added items or buildings can break them in the world, so make a backup before removing mods.

Don't have a server yet? Rent a Project Zomboid server on Lobby Maker — it is ready in about a minute, and mods work exactly as described above.