Project Zomboid Build 41 vs Build 42: which should I run?

Build 42 is the default stable release. Most new servers and players should run Build 42. Choose Build 41 only when you have a clear reason to stay on the older branch.

Quick recommendation

Situation	Run
New server / new world	Build 42 (default)
Existing Build 41 world you want to keep	Build 41 (legacy41)
Mods that only support Build 41	Build 41 (legacy41)
Mods updated for Build 42 (or no mods)	Build 42
Mixed group — some on B41, some on B42	Pick one build for everyone — they cannot mix

Build 42 (stable default)

• Steam: Default Public Version
• AleForge: leave Steam Beta Branch blank
• Best for new playthroughs and current multiplayer features
• No beta opt-in required

See How do I update my Project Zomboid server to Build 42?.

Build 41 (legacy41)

• Steam: select legacy41 (Build 41.78.20)
• AleForge: set Steam Beta Branch to legacy41, then Reinstall Server
• Use this to keep an old world or B41-only Workshop mods
• Every player must also use legacy41 or they cannot join

See How to stay on Project Zomboid Build 41 (legacy41).

Saves and mods

• Build 41 and Build 42 worlds are not interchangeable
• Always create a backup before changing branches
• If the server jumped to B42 by accident, restore a B41 backup, then set legacy41 again before starting
• Install mods that match your build — see How to Add Mods to a Project Zomboid Server

Still unsure?

• Starting fresh with friends → Build 42
• Deep into a B41 map or dependent on unupdated mods → Build 41 until you are ready to wipe and move

Server and clients must always be on the same build.