Project Zomboid 42.20.1 Hotfix Fixes Multiplayer Lag and a Memory Leak
The hotfix also adds mod support for .json files and addresses language-related multiplayer errors and Build 41 world compatibility.
Project Zomboid has received its 42.20.1 stable hotfix, which focuses on multiplayer server performance, memory use, and several compatibility problems. The Indie Stone announced the release in a Steam announcement on August 5.
The developers do not expect the update to break existing saves. If a bug appears, players should try to reproduce it on a fresh save with no mods before sending a report through the bug reports forum.
The hotfix follows the broader Build 42.20.0 stable release, which brought a large map pass and a wide range of system changes. Version 42.20.1 now puts its attention on multiplayer reliability, including chunk unloading problems that caused lag on busy servers. It also targets memory issues that could hurt performance or cause crashes during longer sessions.
Project Zomboid 42.20.1 Patch Notes
The multiplayer fixes cover anti-cheat validation, server lag, language-related crashes, vehicle visibility, and the transition between Build 41 and Build 42. Separate fixes address memory handling and rare exploration errors. Mod authors also gain the ability to write .json files, while translation files now handle percent symbols correctly.
MP
- Improved Lua checksum validation for multiplayer anti-cheat
- Fixed an issue that caused significant performance problems with chunk unloading on multiplayer servers
- This should fix most of the bugs players were getting on high-pop servers due to server lag
- Fixed errors and crashes that could occur when selecting Multiplayer while certain languages were selected
- Fixed an issue where vehicles could temporarily disappear for players after another player disconnected
- Fixed an issue that would allow broken B41 worlds to be hosted on B42 servers
- Fixed an issue where players switching from b41 to B42 could be met with a missing menu
FIXES
- Improved memory usage by reusing discarded world data
- Fixed a memory leak that could lead to performance degradation and crashes over time
- If you continue to encounter an out of memory error in a new save, please submit a bug report with your logs and profiler video from debug so the team can investigate
- Fixed a rare exception that could occur during exploration
TECHNICAL/DEBUG
- Added the ability for mods to write .json files
- Fixed percent symbol handling in translation files
- Mod translations should use %% to display % characters
As always, discussions regarding this update can be found pinned to the Project Zomboid Discussions Forums here.
Have you run into any of these issues in Build 42.20.0? Share your thoughts in the comments, and follow us on X, Bluesky, YouTube, or Instagram.
