How to add mods to your Project Zomboid server

Steam Workshop mods (items, tweaks, vehicles, interface changes). Each Workshop item contains one or more mods, and every mod has its own text ID that is different from the Workshop number.

Back up first. See How to back up and restore your Project Zomboid world.

Add a mod

1. Find the Workshop item number: it is the number at the end of the mod's Steam Workshop URL (steamcommunity.com/sharedfiles/filedetails/?id=3436537035).
2. Find the Mod ID: authors usually list it on the Workshop page as 'Mod ID'. It is not the mod's display title, and it contains no spaces.
3. Open Settings, then Game Settings. Put the Workshop item numbers in Steam Workshop Item IDs, separated by semicolons with no spaces, for example 3436537035;2392709985. If your server has a Workshop tab you can add the item numbers there instead.
4. In Workshop Mod IDs (load order matters), put the Mod IDs separated by semicolons, for example UsefulBarrelsMP;AnotherMod. Downloading an item does NOT enable it: a mod only loads if its ID is listed here, and every mod listed here must also have its item number in Steam Workshop Item IDs.
5. Order the Mod IDs so any library or framework mod that another mod depends on comes first. Mods load left to right and later ones override earlier ones.
6. Restart the server. It downloads and updates the listed Workshop items itself on every start.
7. Check the console at start: it lists the requested Workshop items, the ones that were verified and applied, and the Mods list, and warns if only one of the two fields is filled.
8. Use the two settings fields for all of this and do not edit the Workshop lines in the server .ini file, because the panel rewrites them at every start.
9. To remove a mod, take its Mod ID out of Workshop Mod IDs and its number out of Steam Workshop Item IDs, then restart. Removing a mod that added items, vehicles or other content can leave missing or broken things in an existing world. Take a backup first and remove one mod at a time.

Players need the same mods

Everyone who joins needs the same mods and versions as the server.

Check it worked

Once the server has restarted, read the Console. A mod that loaded shows up during startup, and problems show under Errors and Warnings. See How to use the console and run commands and How to add mods, plugins and modpacks.

If the server stops after you add a mod, remove the newest mod or restore your backup. See How to fix a server that will not start.