Build 42 multiplayer: where it actually is right now
Let me set expectations before we go any further. Build 42's multiplayer is not a finished, stable release. The single-player side of Build 42 landed on the unstable branch in December 2024, and multiplayer finally joined it on the unstable branch in December 2025 as version 42.13. As I'm writing this in April 2026, there is still no stable Build 42 MP release date. The Indie Stone have been clear that what we have is a WIP stress-test build, and they explicitly recommend whitelisted servers and keeping player counts at or below 20.
So this guide is aimed at one specific scenario: you and a small group of friends (four to six people works best) want to jump on the unstable branch together and play with Build 42's new systems today, while accepting that things will break, save formats may change, and some mods won't work. If you're trying to run a public, production-grade Zomboid server right now, honestly, stick with Build 41 stable. It's the boring answer and it's the right one.
Caveat up front. Build 42 MP is on the unstable branch only. Expect bugs, performance issues, occasional wipes, and mods that lag behind the branch. The Indie Stone recommend small, whitelisted groups. Everything below assumes you're opting into that.
If you just want a stable co-op server, our Project Zomboid server hosting guide for 2026 covers the Build 41 path instead.
Switching a LOW.MS server to Build 42 unstable
On LOW.MS this part is easy. Inside TCAdmin at control.low.ms, open your Zomboid server and use the Switch to Latest Experimental button in the sidebar to move the install onto the unstable branch. If you want to roll back to Build 41, the Switch to Stable button next to it does the opposite. Either way, take a backup first — save formats between the two branches are not guaranteed to be compatible.
A quick note on mods: the Mod Manager in the panel will list whatever's available for the branch your server is currently running, but a lot of popular Zomboid mods haven't been updated for Build 42 yet and are still B41-only. Check each mod's workshop page before you wire it into a Build 42 server.
What's actually new in Build 42
Rather than list every change, I want to focus on the things that meaningfully alter how a small group plays together. Everything here is cross-checked against pzwiki.net/wiki/Build_42 and the Indie Stone's December 2025 post.
Crafting, reorganised by discipline
The big one. Build 42 rebuilds crafting around distinct disciplines tied to skill levels, rather than the flat "combine in inventory" approach from Build 41. The confirmed disciplines include Blacksmithing, Carpentry, Masonry, Pottery, Glassmaking, Tailoring, Knapping, Carving, Welding, Electrical, Mechanics, and Cooking. Some of these are new, some are deeper reworks of skills that already existed.
What this means in practice for a group of four to six: there is finally a reason for people to pick lanes. If one friend leans into Blacksmithing and another into Masonry, you'll get access to higher-quality gear and stone-built structures far faster than if everyone grinds the same generic tree. It's not a rigid class system and nothing stops you switching, but the XP curves are deep enough that specialising pays off.
I'll be honest — the "crafting tiers" framing you'll see floating around in some early coverage oversells this. There is no hard Tier 1/2/3 gating with uncraftable factory machines. It's more mundane than that: higher-skill recipes unlock better outputs in each discipline, and some late-game workflows want proper workstations you've built yourself.
Animals and a basic livestock loop
Build 42 adds animals as a first-class system. The ones that matter for a small co-op group:
- Chickens — lowest effort, give eggs, can be butchered for meat
- Pigs — hardy, eat scraps, good meat yield
- Sheep — slower return, but you get wool for tailoring as well as meat
- Cows — highest maintenance and take a long time to mature in real-time, but give milk and a lot of meat once they do
- Deer and rabbits in the wild, for hunting and leather
Animals have needs — food, water, shelter — and you do have to manage them, but don't expect a deep veterinary simulation. Keep them fed, keep them penned, keep zombies away from the fence. For full details on each species, pzwiki.net/wiki/Animal is the most reliable reference.
In a small group this gives the "farmer" role something real to do. One person running a chicken coop and a small pig pen can cover a big chunk of the group's food without anyone having to touch canned beans again.
Basements, sub-levels, and more vertical space
Build 42 adds basements and sub-levels to some buildings as part of the map rework, and raises the vertical cap to 32 floors including those underground levels. These are authored additions to the map, not randomly-drawn-per-playthrough layouts, so don't expect a fresh basement every wipe — the same building will have the same basement.
The practical upshot: there's more map to explore, some buildings have loot and space you didn't have access to before, and tall structures let you build vertically in a way Build 41 didn't really allow. It's a genuinely nice change for groups who like base-building as part of the gameplay loop.
Running a small Build 42 MP group
Server size and admin setup
Keep it small. Four to six players is a sweet spot on the unstable branch — enough for meaningful division of labour, few enough that a single desync or crash doesn't ruin everyone's evening. The Indie Stone's own guidance is to stay at or below 20 and to whitelist. I'd go further and say don't bother opening to the public until the stable 42 release lands.
Whitelist the server, make sure admin accounts are set up before anyone joins, and agree up front on what happens if saves get corrupted — because on unstable, it's a matter of when, not if.
Optional ways to divide tasks
These aren't in-game roles, just a friendly way to split things up in a four-to-six-player group so nobody's stepping on each other's toes:
| Loose role | What they focus on |
|---|---|
| Builder | Walls, fortification, base layout |
| Crafter | One or two disciplines (Blacksmithing, Masonry, Tailoring) |
| Farmer | Crops and the animal pen |
| Scavenger | Loot runs and vehicles |
| Medic | First aid and keeping the group alive |
With four players, one person usually doubles up. With six, you've got room for a dedicated hunter or a second crafter in a different discipline.
Sandbox settings worth tuning
A few settings that make the unstable experience kinder:
- Longer day length (two hours in-game) — the new crafting takes time, and rushed days feel bad
- Default start date — the Knox Event starts on July 9 in the base game. You can shift this in sandbox if you want a longer growing season, but it's a sandbox choice, not a recommendation
- Utilities on for 30 days — gives you breathing room before generators become mandatory
- Slight XP multiplier — 1.25x or 1.5x is reasonable given how many disciplines there are to level
Our server configuration KB article walks through where each of these lives in the config, and the best settings post has preset bundles you can copy.
Performance and RAM
Build 42 is heavier than Build 41. I'm not going to quote a specific number because it depends a lot on player count, animals, and how much of the map you've explored, but plan for more RAM headroom than your Build 41 server needed. If you're sizing a box from scratch, the specs on our Project Zomboid hosting page are a reasonable starting point, and you can scale up from there if you see the server struggling.
If performance does get rough, the first dial to reach for is animal spawn density in sandbox. Entity counts drive a lot of the new overhead.
Communication
Zomboid does not ship with built-in voice chat, so your group will want Discord or similar running on the side. In-game, the built-in chat and radio system are enough for coordination during loot runs — set a shared frequency and you can stay in contact across the map.
Troubleshooting and known rough edges
Because this is the unstable branch, expect:
- Occasional desyncs, especially around vehicles
- Mods that worked yesterday breaking after a hotfix
- Save format changes that may require a wipe between major patches
- Performance dips when the animal system is stressed
If you hit something that isn't obviously a Build 42 bug, our Project Zomboid troubleshooting KB is the right first stop. For Build 42-specific issues, the Indie Stone's December 2025 unstable MP announcement links to their tracker.
So, should you jump in?
If you're a small group who enjoys early-access builds, you're fine with the occasional wipe, and you want to poke at the new disciplines and animals, yes — Build 42 MP on the unstable branch is a fun place to spend a few weekends, and LOW.MS makes switching between branches a two-click job. If you want a stable, public, long-running server, wait for 42 to hit stable and stay on Build 41 in the meantime. Both answers are fine; they're just answers to different questions.
Our getting started KB covers the basics of connecting either way.