B42 Server Not Loading Workshop Mods? The 5 Causes (and Fixes)

The single most common Build 42 server problem right now, as of 42.20: the server starts fine, but Workshop mods don't load — no mod content in game, no errors that make sense, sometimes no mods visible at all. Nine times out of ten it's one of five causes, and the first one on this list accounts for most of them.

1. Your mods are B41 mods

Build 41 mods do not work on Build 42. The engine, the map format, the crafting system and much of the modding API changed. When multiplayer returned in mid-2026, everyone's four-year-old mod list came with it — and none of it loads.

How to check: open the mod's Workshop page. B42-compatible mods are tagged Build 42 (many mods now maintain separate B41 and B42 versions, or a single item with both builds inside). If the mod's last update predates 2025 and says nothing about B42, assume it's B41-only.

The fix is unglamorous: rebuild your list from mods that explicitly support B42. The ecosystem has been catching up fast since the stable release, and the big library mods and QoL staples mostly have B42 versions now — but a 100-mod B41 list will not survive contact with B42 intact.

2. The ini syntax is wrong (semicolons, and two lists that must agree)

Server mods are declared in servertest.ini in two separate keys, and both must be right:

WorkshopItems=2200148440;2857548524;3009299155
Mods=Brita;tsarslib;SomeModID

• WorkshopItems = the numeric Workshop IDs — the number in the mod's Steam URL. This tells the server which Workshop items to download.
• Mods = the Mod IDs — short string names. This tells the server which mods (from inside those items) to actually enable.
• Both lists are semicolon-separated. Commas silently break the list.
• One Workshop item can contain several Mod IDs (a mod plus its library, or B41+B42 variants). Enabling the item but listing the wrong Mod ID from inside it is a classic silent failure.

Where to find the Mod ID: it's usually printed in the Workshop item's description ("Mod ID: Brita"), and it's always in the mod's mods/<name>/info.txt once downloaded. If a mod ships separate B41/B42 Mod IDs, use the B42 one.

3. Steam's download stalled

The server downloads Workshop items through SteamCMD on boot. Steam sometimes quietly stalls a Workshop download or serves a stale version, and the server then boots without the mod (or with an old broken build of it). Server admins' standard fix sequence:

1. Restart the server once — most stalls clear on a fresh boot's update check.
2. If a specific mod is stuck, delete its folder from the server's Workshop cache (under the server's steamapps/workshop/content/108600/<workshop-id>/ — app 108600, the game's ID, is used for Workshop content) and restart so it re-downloads clean.
3. Check the mod updated today on its Workshop page — a mod mid-update can be briefly broken for everyone.

4. The load order is wrong

B42 cares about load order more than B41 did, and dependency mods (libraries like tsarslib that other mods build on) must load before everything that needs them. Symptoms of load-order problems: mods present but half-working, Lua errors on boot, items missing their models. This is a big enough topic that it has its own guide — including the auto-sorting mod-manager approach most admins use now.

5. Server and client disagree

If the server loads mods fine but players can't join or see mod content: the joining player's client is missing mods, has different versions of them, or subscribes to the B41 variant while the server runs B42. The server's mod list is authoritative — clients are told what to load on join — but a client whose Workshop copy of a mod is stale or the wrong build will error or desync. Player-side fix: unsubscribe/resubscribe the mod, verify the game is on the same build as the server, rejoin.

A working example, end to end

Say you want Brita's weapon pack (imaginary IDs for illustration):

1. Open the Workshop page. Confirm Build 42 support. Note the Workshop ID from the URL (say 2200148440) and the Mod ID from the description (say Brita).
2. Check its dependencies section — it needs tsarslib (Workshop 2857548524, Mod ID tsarslib).
3. Stop the server. Edit servertest.ini:

   WorkshopItems=2857548524;2200148440
   Mods=tsarslib;Brita
   

   (Library first, in both lists.)
4. Start the server, watch the console: you should see the Workshop items download, then the mods initialise without Lua errors.
5. Join and verify. If it half-works, it's load order or a stale client — see #4 and #5.

Reading the boot console like an admin

The server console during boot is the only honest witness, and three moments matter:

1. Workshop acquisition — each item in WorkshopItems logs as it's checked/downloaded. An item that never appears here was never requested: syntax problem (semicolons!) or wrong ID.
2. Mod initialisation — each Mod ID from Mods logs as it loads. Present in pass 1 but absent here = the Mod ID is wrong (or the B41-only variant from inside a dual-build item).
3. Lua errors — a red block naming a mod's .lua file right after a list change is a dependency/order failure ninety percent of the time; the named mod loaded before something it needs.

Boot cleanly through all three and remaining problems are client-side, not server-side — which changes whose machine you debug.

Removing a mod safely

Adding is reversible; removing from a live world is the operation that deserves respect. An integrated mod (new items, vehicles, map areas) has objects woven into your save, and pulling it strands them — usually harmless holes, occasionally errors around what it left behind. The safe sequence: backup first, remove from both ini keys, boot, and have players check their bases and vehicles before you call it done. For a heavily-integrated overhaul mod, honestly consider whether the mod's removal is worth more than the world — sometimes the answer is a fresh map.

Frequently Asked Questions

Why did all my mods break when I moved to Build 42?

Because B41 mods are incompatible with B42 — different engine internals, different map, changed modding API. Every mod needs a B42-tagged version. This is the top cause of "server loads no mods" as of 42.20.

Are WorkshopItems and Mods separated by commas or semicolons?

Semicolons, in both keys. WorkshopItems=A;B;C and Mods=X;Y;Z. A comma-separated list fails without a clear error, which is why it's such a common trap.

Where do I find a mod's Mod ID?

The Workshop item's description usually states it ("Mod ID: ..."), and it's always in info.txt inside the downloaded mod folder. It is not the same thing as the numeric Workshop ID in the URL — the ini needs both, in their respective keys.

Do players need to download the mods too?

Clients auto-download the server's Workshop mods on join, but they must own the game on Steam and be on the same build (B42) — and a stale or wrong-branch Workshop subscription on the client side still causes join errors. Resubscribing usually clears it.

If you'd rather pick mods and have the ini syntax handled for you, our managed Project Zomboid hosting runs B42 servers with full file access — edit the ini yourself or ask support to sanity-check your mod list.