How to read a Minecraft server crash report

A crash report looks like a wall of text, but only a few lines matter. Once you know where to look, most crashes take a minute to understand.

Where it is

The server writes a file in the crash-reports folder when the game itself crashes. Other failures, like a plugin that cannot load, do not make a file: they appear in the console and in logs/latest.log. Look at both.

On Saryno, press Check for problems in the Performance tab. It reads the newest crash report and the log, names what it recognises, and offers to remove a plugin that is at fault. The rest of this page is for when you want to read it yourself.

The shape of a crash report

Every report starts with a time, a short description, and a long stack trace: a list of the code that was running, with the newest call first. The key parts are:

1. Description. One line, like "Ticking entity" or "Exception in server tick loop".
2. The first Caused by: line. This is the actual problem. Ignore the lines around it at first.
3. Package names in the trace. A line like at com.example.shop.ShopPlugin.onEnable tells you which plugin was running.
4. System details. The Java version, memory and the list of plugins or mods.

The common causes

• Error occurred while enabling X. Plugin X threw an error while starting. Update it, or check that it supports your Minecraft version.
• Could not load 'plugins/X.jar'. The file is damaged, built for a different server type, or needs another plugin.
• UnsupportedClassVersionError or Unsupported class file major version. Something was built for a newer Java than you run. Pick an older release of it, or move to a newer Minecraft version, which brings a newer Java.
• java.lang.OutOfMemoryError. The server ran out of memory. Add memory, lower the view distance, or remove plugins that hold a lot.
• NoClassDefFoundError or ClassNotFoundException. A plugin needs another plugin or library that is not installed. The missing name is in the message.
• A single server tick took 60.00 seconds. The watchdog stopped a frozen server. Something got stuck: profile it.
• Address already in use. A second copy of the game was still running. Restart it.
• You need to agree to the EULA. The eula.txt file must say eula=true.
• Ticking entity or Ticking block entity. One entity or block in the world is corrupted. The report names its coordinates. Teleport there and remove it, or restore a backup.
• A mod says "requires mod fabric-api". Install the dependency it names.

What to do next

1. Fix the first cause, not the last. One bad plugin can cause pages of errors.
2. Change one thing at a time and restart.
3. If you cannot tell, share the exact lines with someone who can help. On Saryno you can pick lines in the console and press Share to get a link that works for a month, with player addresses blanked.
4. Keep backups so a bad day costs minutes, not a world.

There is a wider list in Minecraft server crash troubleshooting, and the crash log analyzer reads pasted logs in your browser.