java.lang.UnsupportedClassVersionError

Understanding the Error

The java.lang.UnsupportedClassVersionError occurs when you attempt to run a compiled Java class file using an older version of the Java Runtime Environment (JRE) than the one used to compile it. In the context of Minecraft, this usually means your server software (like Paper or Forge) requires a newer version of Java than the one currently active on your instance.

How to fix it

On AwakeNode

Our panel handles Java versions automatically based on the Minecraft version you select. If you encounter this error, it is likely because your server version needs an update.

1. Navigate to the Startup tab.
2. Select the latest version of your preferred server type (e.g., Paper or Forge).
3. Click Apply to update your server files and the associated Java environment.
4. If the error persists, open a Support ticket so our team can verify your startup parameters.

On other hosts / manually

If you are managing your own environment, you must ensure your system's Java version matches the requirements of your server software:

1. Check your current version: Run java -version in your terminal or command prompt.
2. Identify requirements: Check the documentation for your specific Minecraft version (e.g., Minecraft 1.20+ requires Java 17 or 21).
3. Update Java: Install the required JDK/JRE version on your host machine.
4. Update Startup Script: Ensure your startup command points to the correct Java executable. If you are using a custom startup script, verify the -Xmx and path variables are correctly configured for the new Java installation.