Read a Minecraft server crash log, and fix it.

A crash log looks like a wall of Java, but almost all of it is noise. The cause is usually one line, and once you know where to look, most crashes come down to a short list of fixes.

Where the logs are

logs/latest.log: everything from the current or last run. Start here for crashes on startup, plugins that fail to load and errors during play.
logs/*.log.gz: earlier runs, compressed. Useful when the crash happened before the last restart.
crash-reports/crash-<date>-server.txt: written when the game itself crashes, with a description and a full stack trace.
hs_err_pid<number>.log in the server folder: written when Java itself crashes. Rare, and usually memory or the machine.

Find the line that matters

Look for the first error, not the last. One failure often sets off a chain of others. Scroll up to the first ERROR or Exception around the time of the crash.
Read the Caused by: lines. In a stack trace the last Caused by: is usually closest to the real problem.
Look for a plugin’s name in the stack trace. Lines starting at net.minecraft or at io.papermc are the server. A line like at com.example.someplugin points at a plugin, and that plugin is your first suspect.
In a crash report, read Description: first. It names the kind of failure, like Exception in server tick loop, before the trace starts.

Common crashes and their fixes

Wrong Java version

java.lang.UnsupportedClassVersionError: ... has been compiled by a more recent version of the Java Runtime (class file version 65.0), this version of the Java Runtime only recognizes class file versions up to 61.0

The server or a plugin needs a newer Java than the one running it. Class file version 65 is Java 21, which Minecraft 1.20.5 and later require. Most hosting panels let you pick the Java version in the server’s settings.

Missing plugin dependency

Could not load 'plugins/SomePlugin.jar' in folder 'plugins'
org.bukkit.plugin.UnknownDependencyException: Unknown/missing dependency plugins: [Vault]

The plugin needs another plugin that isn’t installed. Install the one named in the brackets, then restart.

Plugin built for another version

[ERROR]: Error occurred while enabling SomePlugin v1.4 (Is it up to date?)

The plugin loaded but broke on startup, usually because it was built for a different Minecraft version. Update it, or check that its supported versions include yours.

Port already in use

**** FAILED TO BIND TO PORT!
The exception was: java.net.BindException: Address already in use

Something else is using the server’s port, often a copy of the server that never shut down. Stop the old process, or change server-port in server.properties.

Out of memory

java.lang.OutOfMemoryError: Java heap space

The server ran out of the memory it was given. Raise it in your host’s panel or the -Xmx flag in your start script. If it keeps happening at any size, a plugin or a huge number of loaded chunks is holding onto memory.

Server stopped responding

[Watchdog Thread/ERROR]: The server has stopped responding!
--- DO NOT REPORT THIS TO PAPER - THIS IS NOT A BUG OR A CRASH ---

One tick took so long that the watchdog stepped in. The thread dump underneath shows what the main thread was stuck on. Look for a plugin’s package in the Server thread section.

EULA not accepted

You need to agree to the EULA in order to run the server. Go to eula.txt for more info.

Common on a brand-new server. Open eula.txt, change eula=false to eula=true, and start the server again.

How Conny works through it

Tell Conny “my server keeps crashing” and it reads the evidence on the server itself:

Opens logs/latest.log and the crash-reports/ folder over SFTP, so there’s nothing to copy and paste.
Lists your plugins, including which ones failed to enable, with the dependencies and API version each one declares.
Checks your server software, Minecraft version and Java version, which is what most “incompatible” crashes come down to.
Fixes the config, the dependency or the setting, with your approval, and explains which line in the log told it so.
Reads the log again once the server is back up, to confirm the error is gone.

Let Conny read the crash for you

Connect your server and Conny goes through the logs itself, then fixes what it finds.

Fix my crashing server How setup works

Nothing to paste: Conny reads the logs on your server over SFTP.

Questions

Where are Minecraft server crash logs?

In the server folder: logs/latest.log for the most recent run, logs/*.log.gz for earlier runs, and crash-reports/ for crash reports written when the game itself crashes. A Java crash leaves an hs_err_pid file in the server folder.

Why does my Minecraft server crash on startup?

The most common causes are the wrong Java version, a plugin missing a dependency or built for a different Minecraft version, the port already being in use, and an unaccepted EULA on a new server. The first error in logs/latest.log says which.

How do I tell which plugin crashed my server?

Look at the stack trace under the first error. Lines starting with net.minecraft or io.papermc are the server itself; a line with a plugin's package name, like com.example.someplugin, points at that plugin.

What does UnsupportedClassVersionError mean?

The server or a plugin was built for a newer Java than the one running it. Class file version 65 means Java 21, which Minecraft 1.20.5 and later need. Switch the server to a newer Java in your host's settings.

Can AI read a Minecraft crash log?

Conny reads the logs and crash reports directly on your server over SFTP, finds the line and plugin at fault, checks versions and dependencies, applies the fix with your approval, and reads the log again once the server is back up.

More guides

Setup guide Connect a server and describe what it should be. Fix server lag Find what is dropping your TPS, then fix that. ChatGPT for servers What it can do, and where it runs out.