UnsupportedClassVersionErrorGeneral 7,805 views
Minecraft 1.20.5+ Fails to Launch: Java 21 Required
Starting from Minecraft 1.20.5, Java 21 is mandatory. Learn how to update with one click in SuperLauncher.
Compatibility:OS: windows, macos, linux•Loaders: vanilla, fabric, forge, neoforge•Versions: 1.21.1, 1.20.4
java-21java-17unsupportedclassversion1.21
Causes of Error & Description
Minecraft Java 21 Mandate Starting with 1.20.5, Minecraft requires **Java 21** (class version 65.0). Launching with Java 17 results in instant termination.
Step-by-Step Solutions
One-Click Java 21 Installation via SuperLauncher
Automated Fix1
Click Auto-Install
Use the SuperLauncher action button below to fetch bundled OpenJDK 21.
2
Relaunch Profile
Launch your 1.21 profile.
Quick Repair in SuperLauncher
Execute action without manual configuration "reinstall_java"
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