Build 42 or Build 41 for a Project Zomboid server in 2026
Updated 2026-11-05
For a new multiplayer server in late 2026, run Build 42. It has been the stable branch on Steam since 29 July 2026, it is what new players install by default, and it is the build The Indie Stone is still working on. Build 41 is worth running for two reasons only: your group has a Build 41 world it wants to finish, or you rely on a mod that has no Build 42 version. Nobody can carry a world between the two, so the choice is really about which world you want to play.
Where does each build stand now?
Build 41 was the version most of the community knew for years, and the one that brought the multiplayer most servers ran on. It now sits on the legacy41 branch on Steam. Its last update we know of was the 41.78.21 security hotfix on 26 August 2026. It is finished, well understood and lighter to run.
Build 42 brought multiplayer back on top of a much bigger game: rebuilt crafting, animals, basements and an expanded map. Multiplayer first appeared on the Unstable branch in December 2025 and reached stable with 42.20 on 29 July 2026. The early stable weeks had problems, including servers hanging on loading the map and memory leaks, which the 42.20.x hotfixes went after. 42.21 reached stable on 28 September 2026 and fixed zombies vanishing and duplicating in multiplayer, along with a Steam authentication exploit. The Indie Stone still publishes known issues, so treat Build 42 multiplayer as solid but still being worked on.
New Build 42 versions now go to the Unstable branch for testing before they reach stable.
Can players on different builds play together?
No. The game and the server have to be on the same build, and the server browser only lists servers on the player's own build. If half your group is on legacy41 and half on the default branch, half of them will not even see the server. Everyone switches in Steam under Properties, then Game Versions & Betas.
Can a Build 41 world move to Build 42?
No. The Indie Stone has said plainly that Build 41 saves are not compatible with Build 42, modded or not. A Build 42 server always starts a new world.
This is the strongest reason to keep a Build 41 server. A world that took months to fortify is not something a group gives up lightly. The usual path is to finish it on Build 41, then start fresh on Build 42 when everyone is ready.
What about mods?
Build 41 has the larger library, built up over years. Build 42 is catching up, but plenty of older mods were never ported. Before you choose, list the mods your group cannot do without and open each Workshop page:
- If the page lists Build 42 support, it will run on Build 42.
- If it lists only Build 41, assume it will not. Some load and then fail in odd ways later.
- Some authors publish the Build 42 version as a separate Workshop item or under a new Mod ID.
On a Build 42 server, every entry in the Mods= line needs a backslash in front, like \ExampleMod. Build 41 uses plain names. Copying a mod list from one build to the other without changing this is a common reason mods do not load.
Does Build 42 need a bigger server?
Yes. Build 42 uses noticeably more memory and processor time than Build 41 for the same group. A useful rule is roughly 2 GB more memory than the same group needed on Build 41.
| Group | Build 41 | Build 42 |
|---|---|---|
| Up to 6 players, no mods | 4 GB | 6 GB |
| Up to 12 players, a few mods | 6 GB | 8 GB |
| 12 to 32 players, long mod list or maps | 8 GB | 12 GB |
A fast processor matters as much as the memory.
So which should you pick?
- A new group or a new world: Build 42.
- A Build 41 world in progress: stay on Build 41 until it is done.
- A must have mod with no Build 42 version: Build 41 for now, and check that mod again after each Build 42 update.
- A public server: Build 42, for the newer anti-cheat and ongoing fixes, with extra memory budgeted.
If you run both, give each world its own save name. A server chooses its world and settings files by name, not by build, so two builds under one name can damage the older world.
Running either build here
Every server on this site offers two server types, Build 42 as the default and Build 41 (legacy) on the legacy41 branch. You can change type later from Settings, and your files stay on disk. Give the new world its own Save name when you do. The Mod IDs setting adds the Build 42 backslash for you and leaves it off on Build 41. Each start checks Steam for updates, and the Java memory limit is set to match your plan. The plan sizes are on plans.