Project Zomboid Build 41 vs Build 42 for servers

For most groups, Build 42 is the right choice. It’s the current stable version of Project Zomboid, it’s what Steam gives players by default, and it gets the fixes and new content. Pick Build 41 only if your group wants to finish a Build 41 world or depends on mods that haven’t moved to Build 42.

The short answer

What changed for servers in Build 42

Build 42 is the biggest update Project Zomboid has had. For a server owner, these are the changes that matter:

• Multiplayer arrived later. Build 42 was single player only at first. Multiplayer came to the testing branch in version 42.13 in December 2025 and reached the stable branch with 42.20 on 29 July 2026.
• A bigger, busier world. Build 42 adds animals and farming with livestock, basements, a reworked Knox County map with new buildings, and much more crafting. More world means more for the server to keep in memory.
• Reworked anti-cheat. 42.20 switched the anti-cheat back on with server-side checks and better logs for admins.
• New server options. For example, you can show or hide map coordinates for everyone, and the player lists show each player’s ping.
• A pre-release branch. Since 42.22, new versions go to a “Pre-Release” branch for at least a week before they reach stable. Server admins can use it to test mods before an update lands.
• Mod changes. Build 42 changed how mods are built, and server files now write mod IDs with a backslash in front. See mods.

The newest stable version on 12 November 2026 is 42.22.2.

Which build to choose

Choose Build 42 if:

• You’re starting a new world.
• Your friends just bought the game or play on the default Steam branch.
• You want animals, basements and the new map.

Choose Build 41 if:

• You have a Build 41 world you want to keep playing.
• Your group depends on big Build 41 mod packs that don’t support Build 42 yet.
• Everyone in your group is happy to switch their game to the legacy41 branch.

Whichever you pick, everyone has to be on the same build as the server. See joining a Build 41 server.

Worlds don’t carry over

The Indie Stone is clear that Build 41 saves won’t work in Build 42. It doesn’t work the other way either. Even within Build 42, saves from the 42.19 testing branch couldn’t load in 42.20.

What this means for your server:

• Moving to Build 42 means a new world.
• Your Build 41 world isn’t lost. Keep it as its own save in Games and switch back to it whenever your group wants. Switching takes a backup first and keeps your address.
• Before you switch builds, download a backup from Backups for safekeeping.

Mods don’t all carry over

Many Build 41 mods don’t work on Build 42 until their authors update them. Some mods have a separate Workshop page for each build.

1. List the mods your group can’t play without.
2. Check each Workshop page for Build 42 support.
3. If a must-have mod is Build 41 only, stay on Build 41 for now, or find a Build 42 replacement.

The Mods tab shows which mods match your server’s build.

RAM: Build 42 needs more

A Build 42 server uses about a third more memory than Build 41 with the same players, zombies and mods. As a rule of thumb:

See the performance guide for what else fills memory.

Switch builds on Wilderack

1. Download a backup of your current world from Backups.
2. Open Settings and change Server type to Build 41 or Build 42.
3. We take a backup and warn you about mods that won’t carry over.
4. Start a new world for the new build, or switch to a save that already uses it in Games.
5. Tell your friends to switch their Steam branch if they need to.

The server installs the right build from Steam. Build 41 uses the legacy41 branch of the Project Zomboid Dedicated Server, the same branch name players use.