Build 42 multiplayer: where it is now
Build 42 is out. The single-player side first landed on the unstable branch in December 2024, multiplayer joined it on the unstable branch in December 2025 as version 42.13, and on 29 July 2026 The Indie Stone put Build 42.20 straight onto the stable public branch, multiplayer included. The current release as I write this is 42.21, which went stable on 28 September 2026 after a week on unstable. The Indie Stone say that's how every update should ship from now on: unstable first, community testing, then stable.
So this guide is for one specific scenario: you and a small group of friends (four to six people works best) starting a Build 42 world together and wanting to get the most out of its new systems. Build 42 is what a new server installs, so the main thing left to be careful about is mods, since plenty of Build 41 mods never got a Build 42 update.
Update, 16 October 2026: This guide was first written while Build 42 multiplayer was still unstable-only. It has been rewritten for Build 42 stable and for the current LOW.MS panel, and the basements section now reflects The Indie Stone's own numbers.
If you're setting up a server from scratch, our Project Zomboid server hosting guide for 2026 covers the basics, and if you're deciding what to do with an existing Build 41 world, our Build 42 stable post covers that.
Choosing your branch on a LOW.MS server
A new LOW.MS Project Zomboid server goes straight onto Build 42 stable (the public branch), so most groups don't need to touch anything. If you want to finish an old Build 41 world instead, or keep playing an unstable 42.19 save, switch the branch in the panel:
- Open your server and go to the Settings tab.
- In the Version row, pick a branch from the dropdown:
legacy41for Build 41,42.19for the last unstable build before stable, orpublicfor current Build 42. - Click Switch branch and confirm. Switching re-downloads the game files, and your server stops and restarts while it does.
Take a backup from the Backups tab first. Build 41 saves won't load on Build 42, and The Indie Stone say Unstable 42.19 saves aren't compatible with 42.20 either, so switching branch is not a way to carry a world across. Every player also has to be on the same branch as the server: in Steam, right-click Project Zomboid, open Properties, and pick the matching branch under Game Versions & Betas.
A quick note on mods: the Mods tab searches the Steam Workshop and installs mods for you, but a lot of popular Zomboid mods are still Build 41 only. Check each mod's workshop page says it supports Build 42 before you wire it into your 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 Build 42 feature overview.
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 as part of the map rework, and lifts the old eight-storey limit: each chunk of the map can now have up to 32 levels, split however the mapper likes between above and below ground. The Indie Stone say Build 42 has 75 unique basements and 400 procedural ones. The unique ones are built into the map. The procedural ones are placed using your world seed, so they change from one world to the next: a house with a basement in one save can have none in another. Basements are one of the new features you can tune in sandbox settings, too.
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. Our interactive Project Zomboid map shows the basements built into the map if you'd rather scout before you build, but it can't show the procedural ones, because those depend on your own world's seed. You'll have to find those in person.
Running a small Build 42 MP group
Server size and admin setup
Keep it small if you can. Four to six players is a sweet spot: enough for meaningful division of labour, few enough that everyone knows what everyone else is doing and a bad night doesn't ruin a dozen people's evening.
Whitelist the server if it's just for friends, make sure admin accounts are set up before anyone joins, and take a backup before every big patch. Build 42 is stable now, but updates that add map content have broken older saves before.
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 Build 42 kinder to a small group:
- 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 server 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 has built-in voice chat, and on our servers it's switched on by default, with directional voice so people sound like they're standing where their character is. Plenty of groups still keep Discord running on the side. In-game, text chat and the 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
Build 42 is stable, but it's a huge build and it's still getting regular patches. Things to watch for:
- Mods that worked yesterday breaking after a patch, especially Build 41 mods that were never updated
- Saves from an older build not loading after an update that adds map content (Unstable 42.19 saves won't load on 42.20), so back up before big patches
- Performance dips when the animal system is stressed
42.21 tackled the worst of the zombie duplication bugs in MP, and zombies vanishing when a player left and re-entered a chunk, so if you've been away since launch it's worth making sure your server is current. 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 42.21 release notes are the place to check what's already been fixed.
So, should you jump in?
Yes. Build 42 is the stable release now, so a new group should start there: the new disciplines, animals and basements are the whole reason to play it together. The one good case for Build 41 is a world you still want to finish, and moving a LOW.MS server to legacy41 is a dropdown on the Settings tab. Whichever you pick, back up first and check your mods.
Our getting started KB covers the basics of connecting.