Launcher problems

java.lang.IllegalArgumentException at org.objectweb.asm.ClassVisitor.<init>

What it looks like in the log

java.lang.IllegalArgumentException @ [org.objectweb]

How to fix it

  1. If you are launching the game through a custom server launcher or unsupported third-party launcher (such as GravitLauncher), switch to the official Minecraft Launcher, Prism Launcher, or Modrinth App.
  2. Reinstall Fabric Loader or Forge using the official installer, or use your launcher's Repair Profile / Verify Libraries option so the libraries/org/ow2/asm/ files are restored to the versions expected by the loader.
  3. If you are already using an official launcher, move any recently added coremods or standalone library JARs out of your mods folder, as one of them may be bundling an old copy of org.objectweb.asm.
LoadersFabric, Quilt, Forge
SeverityStops the game
CategoryLauncher problems

Check your own log

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