On page 7 sections
Briefly
The main reason. The rest and what to do - below
Old Java is running: for example, Java 17 where 21 is needed.
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
This line is printed by Java itself, not the game, so it is only in English. The ellipsis is the path to the file; Java substitutes its own.
- Old Java is running: for example, Java 17 where 21 is needed.
- Install Java with the version you need - see the table on the page “Which Java is needed”. The Mojang launcher and JuxLauncher download the required Java themselves.
- On the server, specify the full path to the desired java in the launch file - otherwise the one that is first in PATH will be launched.
What do you mean, "UnsupportedClassVersionError" in Minecraft?
Java is older than this version of the game or server needs. The numbers in the error are the class file versions: 65 is Java 21, 69 is Java 25.
Why does she write "UnsupportedClassVersionError"?
Old Java is running: for example, Java 17 where 21 is needed.
How to fix "UnsupportedClassVersionError"?
Install Java with the version you need - see the table on the page “Which Java is needed”. The Mojang launcher and JuxLauncher download the required Java themselves.
- Insufficient memory
- Could not reserve enough space for object heap
- No supported graphics backend was found
- Graphics device not supported
- Errors in data sets
- Problems reading the world folder
- Unable to connect to server
- Unknown server
- Timed out
- Connection lost
- End of thread
- Network protocol error
All errors What Java is neededServer startup file
Error texts are from the localization of Minecraft 26.3 word for word; reasons and advice are editorial.