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Fabric API Missing

A Fabric mod will not load because Fabric API is not installed. Fabric API is a core library most Fabric mods depend on, adding it to the mods folder resolves the error.

What does this error mean?
Fabric Loader is minimal by design. Fabric API provides the shared hooks and interfaces the majority of mods use. 'Fabric API not found' means a mod needs it but it is absent from your mods folder. 
Fabric API not found
Most Common Causes
  • Fabric API not installed at all.
  • A Fabric API version not matching your Minecraft version.
  • Confusing Fabric Loader with Fabric API (they are separate).
  • Fabric API installed on the client but not the server.
  • A typo'd or partial install.
How To Diagnose
  1. Check the mods folder for the fabric-api jar.
  2. Confirm its version matches your Minecraft release.
  3. Verify it is present on the server, not only the client.
  4. Read the log for the specific mod requesting it.
Recommended Fixes
  • Install Fabric API
    Download the Fabric API build for your Minecraft version and place it in mods/.
  • Match the version
    Use the Fabric API release that targets your exact Minecraft version.
  • Install on both sides
    Add Fabric API to the server too, not just the client, when mods need it server-side.
  • Keep it updated
    Update Fabric API alongside your mods when you upgrade.
Analyze My Log
Frequently Asked Questions

No. Loader runs mods, API is a library most mods require. You usually need both.

Most do. A few standalone mods do not, but installing it is the safe default.

From the official Fabric API page on Modrinth or CurseForge, matched to your version.