Minecraft — troubleshooting
The most common errors, their causes and quick fixes. Always start by reading the console from the top — the first error is usually the real one.
On this page
Server won't start
| Console message | Cause and fix |
|---|---|
| UnsupportedClassVersionError | Wrong Java version. Change the Java image under “Startup” — see Software, version & Java. |
| You need to agree to the EULA | Accept the EULA in the panel or set eula=true in eula.txt. |
| FAILED TO BIND TO PORT | server-port was changed in server.properties. Restore the port from the Network tab. |
| Unable to access jarfile | The server jar is missing or misnamed under “Startup”. Reinstall the software or fix the .jar file name. |
| Could not load 'plugins/…' | The plugin doesn't match the server version or a dependency is missing. Remove it or install the required plugin. |
Crashes and memory
| Message | Cause and fix |
|---|---|
| OutOfMemoryError | Not enough RAM for the world/mods. Lower view-distance, limit entities or upgrade your plan. |
| Can't keep up! Is the server overloaded? | The server can't keep up with ticks. Run a spark profiler report and see what's causing the load — Optimization. |
| Watchdog / server has stopped responding | A single tick took too long — usually a plugin or a farm. Look for the plugin name in the stack trace. |
Players can't join
- “Outdated client / server” — the player's game version differs from the server. Consider ViaVersion.
- “Failed to verify username” — the player has a non-premium game with
online-mode=true, or Mojang's servers are having issues. - “You are not white-listed” — add the player:
whitelist add Name. - Timeout — check that the server is running and the player is using the correct
IP:PORT.
Sharing a log
Upload logs/latest.log to mclo.gs and paste the link in your ticket. The site hides IP addresses automatically.
Was this page helpful?