---
title: "prism launcher unsupported class file major version | Prism Launcher"
description: "Fix \"unsupported class file major version\" in Prism Launcher: Java runtime, memory slider, and instance log. Download Prism Launcher from /download."
canonical: https://prismlauncher.ink/java/unsupported-class-version
updated: 2026-10-17
---

# Prism Launcher unsupported class file major version

Fix "unsupported class file major version" in Prism Launcher: Java runtime, memory slider, and instance log.

## Facts (2026-10-17)

- **Issue:** unsupported class file major version
- **First check:** Edit Instance → Settings → Java

## unsupported class file major version

"prism launcher unsupported class file major version" is a common support search. Read the instance log before reinstalling the pack.

Match Java to the Minecraft version (8 / 17 / 21). Do not give a 1.16 pack Java 21 unless the pack says so.

Installer: [/download](https://prismlauncher.ink/download).

## FAQ

### Auto-download Java?

Prism can fetch a matching runtime. Point the instance at that install.

## Related

- [Prism Launcher Java & JVM Configuration](https://prismlauncher.ink/java)
- [Prism Launcher How-To Tutorials](https://prismlauncher.ink/howto)
- [Java 21 (64-Bit) for Minecraft 1.20.5 & 1.21+](https://prismlauncher.ink/java/java-21-temurin-minecraft-1-20-5-1-21)
- [Troubleshooting: Java 21 (64-Bit) for Minecraft 1.20.5 & 1.21+](https://prismlauncher.ink/java/java-21-temurin-minecraft-1-20-5-1-21-troubleshooting)
- [Java 17 (64-Bit) for Minecraft 1.18 – 1.20.4](https://prismlauncher.ink/java/java-17-temurin-minecraft-1-18-1-20-4)

## Download

Free and open source: [Download Prism Launcher](https://prismlauncher.ink/download)

Markdown mirror: https://prismlauncher.ink/java/unsupported-class-version.md