Project Zomboid Mods on a Build 42 Dedicated Server

To add Workshop mods to a Project Zomboid Build 42 dedicated server, put each mod's Workshop ID on the WorkshopItems= line and its Mod ID on the Mods= line of the server's .ini file, separated by semicolons, then restart so the server downloads them. Only mods built for Build 42 load on the current stable version, 42.21, because Build 42 moved mod files into a common folder and version folders such as 42.

Everything below was checked on 25 October 2026 against The Indie Stone's patch notes, the official PZwiki and the mod pages it mentions.

What changed for mods in Build 42

A Build 41 mod keeps its media folder and its mod.info file directly in the mod folder. Build 42 splits them, according to the PZwiki page on mod structure, which is revised for 42.21.0:

Contents/mods/MyMod/
    common/        models, textures and other shared files
        media/
    42/            mod.info and the code for Build 42
        media/
        mod.info

Three rules from that page matter when you run a server:

1. A mod needs a common folder or a version folder to be recognized in Build 42. A mod with nothing but a top-level media folder is a Build 41 mod and will not show up. Since 42.15.0 one of the two folders is enough.
2. The game loads common first and then the version folder closest to the running build, which overrides files with the same path. A folder called 42 counts as 42.0 and 42.12 as 42.12. A third number is ignored, so 42.1.5 is read as 42.1.
3. Build 41 and Build 42 copies can share one Workshop item. The Build 42 structure sits one folder deeper, so the two never clash. That is why a mod page can say "B41 and B42" while your server only uses the 42 part.

If a Workshop page only talks about Build 41, or the downloaded mod has neither a common folder nor a version folder such as 42, the mod will not load on a 42.21 server. Build 41 worlds do not come along either; our Build 42 stable guide covers that move.

The three IDs a mod can have

Most "mod not loading" problems come from putting the right number on the wrong line.

The examples are the real IDs of Extraction Mode, whose Workshop page ends with exactly these three lines. Mods uploaded with the in-game uploader print their Workshop ID the same way.

Things that catch people out:

• One Workshop item can hold several mods, each with its own Mod ID. The Workshop ID goes on its line once; add only the Mod IDs you want active.
• Dependencies need both IDs as well. A require= line in mod.info names Mod IDs that must be active too, and their Workshop items have to be on WorkshopItems=.
• Copy every ID exactly as written, capitals included.

If a page lists no Mod ID, subscribe in Steam and open Steam/steamapps/workshop/content/108600/<Workshop ID>/ on your PC. Each mod inside has a mod.info, and its id= line is the Mod ID.

The lines in the server's .ini

A dedicated server reads servertest.ini in the Zomboid/Server folder, next to servertest_SandboxVars.lua, unless it runs under another server name, in which case both files carry that name (PZwiki, Dedicated server). A server with one gameplay mod and one map mod looks like this:

WorkshopItems=1111111111;3785397275
Mods=YourModID;ExtractionMode
Map=ExtractionMap;Muldraugh, KY

The first ID and YourModID are placeholders. Separate entries with semicolons, as in the wiki's own example WorkshopItems=514427485;513111049. Muldraugh, KY is the vanilla map and stays on the Map= line; our Build 42 map guide covers its towns and spawn regions. Extraction Mode's page tells you to place the hideout map before the vanilla maps.

Hosting guides disagree on one detail: some say Build 42 needs a backslash in front of every Mod ID (Mods=\YourModID), others say current Build 42 versions read plain IDs again. Neither The Indie Stone's patch notes nor the wiki's server settings page show the format as of 25 October 2026. So do not guess. Let the game write the lines for you:

1. On your PC, subscribe to the mods in Steam and start Project Zomboid 42.21.
2. Open Host, then Manage Settings, and create or edit a settings file.
3. Add the Workshop items, then the mods, then set the map order in the map section, and save.
4. Open Zomboid/Server on your PC (on Windows that is C:\Users\<you>\Zomboid\Server) and copy the WorkshopItems=, Mods= and Map= lines from the .ini file you just saved.
5. Stop the server, paste the three lines into its .ini through the panel's file manager or over SFTP, and start it again.

The server downloads the Workshop items when it starts, and players' games fetch the same items when they join, as the wiki notes. Most settings can be reloaded live with the reloadoptions admin command, but a mod change needs a full restart.

Load order

The PZwiki page on load order is blunt: it "is often presented as important when it really isn't". For gameplay mods, order only matters when two mods ship a file with the same relative path, such as a Lua or script file under media/lua or media/scripts. Then the mod that loads later overwrites the other one's file. Well-made mods keep their files in a subfolder named after the mod, which is the wiki's fix for exactly this clash.

Maps are the exception. Two map mods that touch the same cells conflict, and the wiki says load order cannot fix that: one of the two ends up with broken parts. Map pages often list their cells (Maplewood's says "B42 Cells: 31x32, 31x33, 32x32, 32x33"), so compare those before you combine maps, or check the pair with Map Mod Manager or PZ Map Analyser, the tools the wiki names for this.

Two more habits that save a world:

• Do not drop a map mod into a world that is already running. Fort Preston, for example, says not to install it on an ongoing save or server.
• Back up Zomboid/Saves before every mod change. The wiki's advice for changing mods in an existing world starts with exactly that.

Updating mods without kicking everyone

Steam updates your players' copy of a mod as soon as the author pushes a new version. The server keeps its old copy until it restarts and downloads the update, and until then players with the new files can be refused at login. The admin command checkModsNeedUpdate tells you whether a mod has been updated and writes the answer to the server log (admin commands). If players still get kicked, our guide to the "File doesn't exist on the client" error goes through the checksum errors one by one.

Game patches can break mods too. 42.20.4 removed the Lua methods loadstring and loadstream to close a security hole, and mods that used them stopped working until 42.21 put both back on 28 September 2026, with an apology to "modders/server admins". After a patch, look at your mods' pages before you restart a busy server.

Lua mods, Java mods and trust

Regular Workshop mods are written in Lua, the only kind of modding The Indie Stone officially supports. Its note on Java mods of 21 October 2026 explains the other kind. Java mods change the game's own code, which is how some recent mods change the game "at a fundamental level", in The Indie Stone's words. They are not officially supported, and they usually need manual installation, downloads from outside Steam or a special loader. The note is blunt about patches: "When we ship new updates, Java-based mods will be fundamentally broken by those updates, without warning." Bug reports are only looked at when the problem happens without mods.

On a server, a Java mod means replacing game files instead of adding a Workshop ID, and the next game update can undo or break it. If you want one on a rented server, ask the host before you start.

Workshop mods need some trust as well. In April 2026 The Indie Stone warned about 14 Workshop mods from one uploader that created malicious files outside the game folder; the uploader was banned and the mods were removed. They had been installed on 500 to 2,200 devices, and only Build 42 branches were affected. A mod that many players already run is reassuring, but in The Indie Stone's words "absolutely is not a guarantee" of safety. Do not put anything on a server that you would not install on your own PC.

RAM for a modded server

Memory follows how much of the map is loaded more than the number of players, because explored cells stay in memory. Our product page sizes it like this: 4GB for a small group on vanilla or a light mod list, 6GB for a real Workshop mod list and a bigger group, 8GB for heavy modpacks or a long running world where the group has explored several towns. Our Project Zomboid server hosting runs the current stable branch in nine regions, and the Workshop items on your WorkshopItems= line download when the server starts. If you are still comparing hosts, our Project Zomboid hosting comparison sets RAM and monthly prices side by side.

FAQ

Why does a mod work in single player but not on my server? The usual causes: the mod has no Build 42 version, its Workshop ID is on the Mods= line or its Mod ID on WorkshopItems=, a required mod is missing, or a map mod is not on the Map= line. Build the lists with Host and Manage Settings and copy them across.

Do players have to download the mods themselves? No. Players' games fetch the server's Workshop items automatically when they connect. They do need the same versions as the server, so restart the server after a mod update.

Do I need a backslash before Mod IDs on Build 42? Guides disagree, and neither The Indie Stone's patch notes nor the wiki show the format as of 25 October 2026. Save the mod list from the game's own Host settings and copy the Mods= line it writes.

Where does a map mod go on the Map line? Before Muldraugh, KY, which stays on the line. The map's Workshop page gives the folder name and usually the order, such as Map=ExtractionMap;Muldraugh, KY.

Can I add mods to a world that is already running? Gameplay mods, yes, after a backup of Zomboid/Saves. Map mods are best added before the group explores the area they change.

Are Java mods allowed on a dedicated server? The Indie Stone does not support them, they usually need manual installation, and every game update can break them. Stick to Workshop Lua mods unless you are ready to repair the server after each patch.