How to Fix a Project Zomboid Server That Keeps Crashing
Most Project Zomboid server crashes come from a short list of causes. Check them in order — RAM and Java first, then mods and map chunks — and you'll find the problem faster than guessing at random settings.
Out of memory
Project Zomboid runs on the JVM and allocates heap memory at startup. If the heap limit is too low, the server throws an OutOfMemoryError and crashes mid-session. Fix: open jvm.options in the server directory and raise -Xmx — for example, -Xmx6g for 6 GB. Check the log file for 'java.lang.OutOfMemoryError' to confirm this is the cause.
Corrupted map chunks
If a player moves into a map cell that was written incorrectly — usually from a crash mid-save or a disk I/O error — the server will crash when it tries to load that chunk. Fix: locate the affected cell coordinates in the log (look for an exception with a map_X_Y filename), then delete that map_X_Y.bin file from Zomboid/saves/Multiplayer/ServerName/. The chunk will regenerate on next load.
Java version mismatch
Project Zomboid requires Java 17 specifically. Running an older or newer JVM can cause cryptic startup errors, class loader failures or silent crashes. Fix: run `java -version` on the server. If the output is not Java 17, install OpenJDK 17 and set JAVA_HOME to point to it before starting the server. Most distros have `openjdk-17-jdk` available in their package manager.
Mod conflict
Workshop mods are the most common source of PZ server crashes after the server is otherwise running fine. A single bad mod can cause NullPointerExceptions that crash the whole server. Fix: check the server log for 'NullPointerException' or 'ERROR' lines that reference a mod name or Workshop ID. Disable mods one by one (or in halves) to isolate the offender, then check the mod's Workshop page for known issues.
Lua error from a mod or script
PZ runs a live Lua sandbox for game logic, and any unhandled Lua exception can bring down the session. Fix: grep the server log for 'LuaError' or 'LuaException'. The log will include the script file and line number. The fix is usually disabling or updating the mod that owns that script — check for a newer version on the Workshop.
Database lock file left from unclean shutdown
When the PZ server crashes hard or is killed without a clean shutdown, it can leave a db.lock file in the save folder. On the next start, the server sees the lock and refuses to open the database, which causes an immediate crash-on-startup. Fix: navigate to the save folder (Zomboid/saves/Multiplayer/ServerName/) and delete db.lock, then restart the server.
Simulation overload — too many players or zombies
Project Zomboid simulates the full map server-side at all times. A high MaxPlayers value combined with a high ZombieCount setting pushes the simulation load beyond what the CPU can sustain, causing cascading slowdowns that eventually crash the server. Fix: reduce MaxPlayers and lower ZombieCount in the server sandbox settings. Reducing PopulationMultiplier in the sandbox settings gives you fine-grained control over zombie density without capping players.
FAQ
Where are Project Zomboid server logs stored?+
Does Project Zomboid need Java to run a server?+
Can mods cause Project Zomboid server crashes?+
How do I clear a corrupted map chunk in Project Zomboid?+
Host your Project Zomboid server from €12/month
CoalHost runs PZ servers with the right Java runtime, RAM headroom, Workshop mod support and auto-backups so you have a rollback when things go wrong.
View Project Zomboid Hosting →