Server crashes can be caused by various factors including insufficient memory, plugin conflicts, corrupted worlds, or Java issues. This guide will help you identify and fix the root cause.

Analyze Crash Reports

Start by examining the crash report to understand what caused the failure:

Check the crash-reports/ folder for recent crash files
Open the latest .txt crash report file
Look for the "Description" section at the top
Find the stack trace showing where the error occurred

Common crash indicators:

OutOfMemoryError: Java heap space
NullPointerException
ClassNotFoundException
ConcurrentModificationException
StackOverflowError

Check Server Logs

Examine server logs for warnings and errors leading up to the crash:

Open logs/latest.log or the most recent log file
Look for [ERROR] and [WARN] messages before the crash
Check for plugin-related errors or exceptions
Note any patterns in timing (specific times, player actions, etc.)

Enable debug logging temporarily if crashes are intermittent: set debug=true in server.properties

Fix Memory-Related Crashes

OutOfMemoryError is one of the most common crash causes:

Increase allocated RAM:

# Current allocation
java -Xmx2G -Xms2G -jar server.jar

# Increased allocation (adjust based on available RAM)
java -Xmx4G -Xms4G -jar server.jar

Add garbage collection optimizations:

java -Xmx4G -Xms4G -XX:+UseG1GC -XX:+ParallelRefProcEnabled \
-XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions \
-XX:+DisableExplicitGC -jar server.jar

Identify Plugin Conflicts

Plugins are a common source of server instability:

Safe Mode Test: Remove all plugins temporarily and test stability
Binary Search: Add plugins back in groups of 5-10 until crashes return
Version Check: Ensure all plugins are compatible with your server version
Dependency Check: Verify required dependencies are installed
Update Plugins: Use latest stable versions of all plugins

# Temporarily disable plugins by renaming the folder
mv plugins plugins_backup
mkdir plugins

Fix World Corruption Issues

Corrupted world data can cause crashes during chunk loading:

Backup first: Always backup your world before attempting fixes
Test with new world: Create a temporary world to test server stability
Region file check: Look for corrupted .mca files in world/region/
Chunk regeneration: Use WorldEdit or similar tools to regenerate problematic chunks

Find corrupted region files:

# Look for 0-byte or unusually small files
ls -la world/region/ | grep "\ 0\ "

Resolve Mod Compatibility Issues

For modded servers, mod conflicts can cause crashes:

Version compatibility: Ensure all mods support your Minecraft version
Dependency mods: Install required core mods (Forge, Fabric API, etc.)
Conflicting mods: Check for known incompatibilities between mods
Update mods: Use the latest stable versions
Test individually: Add mods one by one to identify problematic ones

Check mod descriptions and GitHub issues for known compatibility problems and solutions.

Java and System Issues

Sometimes the problem is with Java itself or system configuration:

Update Java:

Download the latest Java version for your Minecraft version
Java 17+ for Minecraft 1.17+, Java 8 for older versions
Use Oracle JDK or OpenJDK from Adoptium

System resources:

Monitor CPU usage during crashes
Check available disk space (minimum 1GB free)
Verify system has sufficient RAM beyond server allocation
Close unnecessary background applications

Implement Preventive Measures

Set up monitoring and safeguards to prevent future crashes:

Automatic restarts: Schedule regular server restarts (daily or weekly)
Backup automation: Set up automatic world backups before restarts
Resource monitoring: Use tools to monitor RAM, CPU, and disk usage
Log rotation: Prevent log files from consuming too much disk space
Watchdog scripts: Automatically restart server if it crashes

Simple watchdog script example:

#!/bin/bash
while true; do
    java -Xmx4G -Xms4G -jar server.jar
    echo "Server crashed! Restarting in 10 seconds..."
    sleep 10
done

With proper diagnosis and these preventive measures, you should experience significantly fewer server crashes. Regular monitoring and maintenance are key to long-term stability.

How to Fix Minecraft Server Crashes