Corrupted files

Crash on Launch: ClassNotFoundException: org.objectweb.asm.tree.ClassNode

What it looks like in the log

java.lang.ClassNotFoundException: org.objectweb.asm.tree.ClassNode

How to fix it

  1. In third-party launchers such as HMCL or PCL2, open the download settings and switch the download mirror back to the Official source.
  2. Clear your launcher's download cache in its settings menu so it will not restore the corrupted JAR from local cache.
  3. Open your game directory, go to .minecraft/libraries/org/ow2/asm/, and delete the asm-tree folder (or delete the entire org/ow2/asm folder).
  4. Update your launcher to the latest version to ensure file checksum verification is enabled, then launch the profile again or reinstall Fabric/your mod loader so it downloads a fresh copy of the libraries.
LoadersFabric, Quilt, Forge, Neoforge
SeverityStops the game
CategoryCorrupted files

Check your own logDownload tree on 9Minecraft

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