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Wrong Mod Loader

A mod will not load because it was built for a different mod loader than your server uses. Fabric, Forge, and NeoForge mods are not interchangeable, the mod must match the loader.

What does this error mean?
Each loader (Fabric, Forge, NeoForge) has its own mod format. A 'ModLoader mismatch' means you placed a mod for one loader on a server running another, so it cannot be recognized or loaded. 
ModLoader mismatch
Most Common Causes
  • A Fabric mod on a Forge/NeoForge server (or the reverse).
  • Downloading the wrong loader's build of a mod.
  • Mixing loaders in one mods folder.
  • Assuming a mod is cross-loader when it is not.
  • A multi-loader project where the wrong file was chosen.
How To Diagnose
  1. Confirm which loader your server runs.
  2. Check which loader each mod targets.
  3. Read the log for which mod was rejected.
  4. Verify you downloaded the correct loader's file.
Recommended Fixes
  • Get the matching build
    Download the version of the mod made for your server's loader.
  • Use one loader consistently
    Keep only mods for your chosen loader in the mods folder.
  • Switch the server loader
    If you need a specific mod, run the loader it requires instead.
  • Check multi-loader downloads
    On mod pages, pick the correct loader's file explicitly.
Analyze My Log
Frequently Asked Questions

No. They are different formats, a server runs one loader and only its mods.

The download page lists Fabric/Forge/NeoForge, pick the one matching your server.

Some mods publish builds for several loaders, but each build is loader-specific.