criticalJava ErrorsAffects: 1.17+
How to Fix UnsupportedClassVersionError
Fix UnsupportedClassVersionError by installing the correct Java version. Minecraft 1.21+ requires Java 21.
Quick Fix
Install Java 21 for Minecraft 1.21+. Minecraft 1.17-1.20.4 requires Java 17 minimum.
Error Message
java.lang.UnsupportedClassVersionError: has been compiled by a more recent version of the Java RuntimeHow to Fix
1
Download and install Java 21 from Adoptium (adoptium.net)
2
Set the correct Java path in your launcher settings
3
Verify the active Java version: java -version
4
Ensure your launcher is not overriding the Java path to an old version
Common Causes
- Using Java 8 or 11 with Minecraft 1.17+ which requires Java 16+
- Mod compiled with a newer Java version than installed
- System Java version is outdated
Diagnostic Steps
- Open a terminal and run java -version
- If below Java 17, install Java 21 from Adoptium
- Configure your launcher to use the new Java installation
- Restart the launcher and try again
FAQ
Which Java version does Minecraft 1.21 need?
Minecraft 1.21+ requires Java 21. The official launcher bundles this, but third-party launchers may need manual configuration.