Project Zomboid Build 42 Server Setup (Stable since 29 July 2026)

Is Build 42 stable now?

Yes. Project Zomboid 42.20 has been on the public stable branch since 29 July 2026 — multiplayer included. That ends a development phase of more than seven years: Build 41 had been the stable version since December 2021. New servers now start on 42.20 automatically; anyone who wants to stay on Build 41 switches to the legacy41 beta branch.

At RespawnHost a server is online in under 90 seconds. For self-hosting you need dedicated server app 380870 — the unstable beta branch is no longer required, 42.20 is the default.

Milestone	Date
Build 41 goes stable	December 2021
B42 unstable (singleplayer)	17 Dec 2024
B42 multiplayer on unstable	11 Dec 2025 (version 42.13)
Build 42.20 stable, with multiplayer	29 July 2026
Planned next	Hotfixes, late-game patch, “Build 42 Support Update” (rest of 2026)

The demand confirms the expectation: one day after the stable release, on 30 July 2026, Project Zomboid hit its all-time peak of 79,670 concurrent players on Steam — after nearly 13 years in Early Access.

What changes for server owners?

The most important change is not in the player-facing patch notes but in the architecture: the inventory system now runs server-side. Item transfers, container interactions and loot distribution moved from the client to the server, as did all TimedActions. The client only renders — execution happens on the server.

That brings real benefits and a cost:

	What it means
Anti-cheat suite	Speed, Hit, NoClip and Inventory checks run server-side
Fewer desyncs	Dozens of remote player state bugs fixed, NetworkState reworked
Higher server load	What the client used to compute now runs on the server — more RAM and CPU
Better server browser	Filters for modded/full/empty, sorting by ping and player count

How do I stay on Build 41?

The Indie Stone provides a branch specifically for this — explicitly aimed at server owners too:

1. Right-click Project Zomboid in your Steam library
2. Open Properties
3. Under Game Versions & Betas select legacy41

Everyone playing together must use the same branch. The same applies to the server: client and server have to match.

Are my save games compatible?

This needs care — there are two separate cases:

Starting point	Compatible with 42.20?
World from unstable 42.19	No. Additional map content makes existing saves unusable. To keep playing, opt into the 42.19 beta branch
World from Build 41	Plan for a fresh world. To keep the old one, stay on Build 41 via legacy41

What is new in Build 42?

The parts that matter for servers, in numbers:

Area	Scope
Map	Surface area doubled, 1,400 unique buildings, 20,000 new tiles (Build 41: 15,000 in total)
New towns	Ekron, Irvington and Brandenburg, plus numerous smaller locations
Reworked	Riverside, West Point, Rosewood, Fallas Lake, Muldraugh, Ekron, Dixie
Height	Basements, bunkers and panic rooms; up to 32 floors in Louisville
Animals	Sheep, chickens, pigs, cows, rats, rabbits, deer — plus raccoons
Crafting	Masonry, carving, knapping and blacksmithing as new branches, plus workstations
Game modes	Apocalypse (canon), Outbreak, Rising, Extinction
Mods	Official mod manager with load order, dependencies and shareable presets

On top of that: a completely overhauled lighting system, a new firearm aiming system and randomised wilderness at the map edges.

How do you create a B42 server at RespawnHost?

1. Rent a Project Zomboid server — fixed plan or pay-per-use, online in under 90 seconds
2. Pick a plan by player count — entry level is 10 GB, details in the guide How much RAM?
3. Start it — 42.20 is the default, no branch switching needed

Screenshot to follow: version selection 42.20 / legacy41 in the server configuration in the RespawnHost panel

4. Connect: IP and port are in the panel — in game under Join enter the IP and port 16261. Password, PVP and slots are set in servertest.ini.

How do you self-host (SteamCMD)?

The dedicated server is app ID 380870. For 42.20 the default branch is enough:

steamcmd +login anonymous +app_update 380870 validate +quit

To stay on Build 41, append the branch:

steamcmd +login anonymous +app_update 380870 -beta legacy41 validate +quit

• Start: StartServer64.bat (Windows) or start-server.sh (Linux)
• Configs: %USERPROFILE%\Zomboid\Server\ or ~/Zomboid/Server/ — containing servertest.ini and servertest_SandboxVars.lua
• RAM: assigned as a Java parameter via -Xmx in the start script
• Port: 16261 (UDP), range used is 16261–16262

What do we recommend for the switch?

• Back up before switching — not negotiable, see above
• Start with a known mod list: after a jump this large, mods need time to catch up. The new mod manager shows dependencies and conflicts
• Do not cut RAM too close: the server-side inventory costs performance the client used to carry
• Set sandbox rules first: zombies, loot and XP in the sandbox settings guide

Frequently asked questions

Since when is Build 42 stable? Since 29 July 2026 with version 42.20, multiplayer included.

Do I need to switch branches for Build 42? No. 42.20 is the default. A branch is only needed to stay on Build 41 (legacy41) or on unstable 42.19 (42.19).

Can I keep playing my unstable 42.19 world? Not on 42.20 — the new map content makes those saves incompatible. You can continue them via the 42.19 beta branch.

Can I bring my B41 world to B42? Plan for a fresh world on Build 42. To keep an established world, stay on Build 41 via legacy41.

Do I need more RAM than before? Yes. Inventory and TimedActions run server-side now, work the client used to do. That is why our entry plan for Project Zomboid is 10 GB.

Is Project Zomboid on consoles, or does it have crossplay? No. Project Zomboid is PC-only — Windows, macOS and Linux play together, there is no console release.

Related guides

• Server settings (servertest.ini) — PVP, whitelist, mods & ports
• Sandbox settings — zombies, loot & XP
• Admin commands — becoming admin & managing the server
• How much RAM? — finding the right plan