Direct answer

Check the Java version printed by the server startup environment, not the Java installed on your own PC. Select the required runtime/container in the panel, restart fully, and verify it again with the startup log or `java -version` inside that environment.

What it means

The Java installed on the machine may differ from the runtime selected by the hosting panel or startup container.

If you are a player

  • This is a server-side startup problem. Send the owner the exact panel/console error; reinstalling your game client will not fix it.

If you run the server

  1. Read the first Java/JVM error before the final “server stopped” or panel exit-code summary.
  2. Run java -version in the same shell/container/panel runtime that actually launches the server.
  3. Verify the Java release and JVM arguments against the exact server software/version; remove old or copied flags that the current runtime rejects.
  4. Fix startup/runtime selection before changing world or plugin data, because Minecraft may not have started yet.

Current Paper Java requirements

Paper currently documents Java 21 for Paper 1.20 through 1.21.11 and Java 25 for Paper 26.1+. Other server software or older Minecraft versions can require a different Java release, so check that project’s exact version table.

References

Use the documentation for the exact software and release you run. These sources support the settings or diagnostic behavior used in this fix.

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