Error creating Mixin config: JAVA_16 compatibility level not supported on Java 1.8

What the log looks like

java\.lang\.RuntimeException: Error creating Mixin config fabric-rendering-data-attachment-v1\.mixins\.json for mod fabric-rendering-data-attachment-v1
java\.lang\.IllegalArgumentException: The requested compatibility level JAVA_16 could not be set\. Level is not supported by the active JRE or ASM version

How to fix it

1. Check your mods folder and verify that every mod jar (especially Sodium and Fabric API) matches your exact Minecraft version.
2. If you are playing Minecraft 1.16.5, delete any 1.17 or 1.18+ mod files (such as mc1.18.2 jars) and replace them with builds made specifically for 1.16.5.
3. If you are playing Minecraft 1.18 through 1.20.4, install Java 17 (or Java 16 for Minecraft 1.17.1).
4. Open your launcher's profile or instance settings and change the Java executable path from Java 8 (1.8) to your Java 17 javaw.exe, or enable the launcher's bundled Java runtime.

Check your own log