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NeoForge Library Missing

A NeoForge mod fails to load because a required library it depends on is not installed. The log names the missing library, adding it lets the mod load.

What does this error mean?
Many mods rely on shared library mods (config systems, API layers). 'Missing required library' means a dependency library is absent, so the mod that needs it cannot initialize. 
Missing required library
Most Common Causes
  • A required library mod not installed.
  • The library present but at the wrong version.
  • A transitive dependency overlooked when installing the mod.
  • A library built for a different loader/version.
  • An incomplete modpack copy.
How To Diagnose
  1. Read the log for the exact library name and version.
  2. Check the mods folder for that library.
  3. Confirm its version targets your NeoForge/Minecraft build.
  4. Review the mod's dependency list on its download page.
Recommended Fixes
  • Install the library
    Add the named library mod (matching version) to the mods folder.
  • Match the version
    Use the library build made for your NeoForge and Minecraft version.
  • Install all dependencies
    Check the mod page and add every listed library it needs.
  • Use the complete pack
    If running a modpack, install it whole so libraries are not missed.
Analyze My Log
Frequently Asked Questions

A support mod that provides shared code (configs, APIs) other mods build on.

On the mod's download page under dependencies, install each at the matching version.

Libraries are often separate downloads, easy to overlook when adding a mod manually.