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Connection Closed - Mod Rejections

A player on a Forge server is disconnected with 'Connection closed - mod rejections'. During the Forge handshake, the server compared mod lists and found the client's does not match, so it closed the connection.

What does this error mean?
Forge negotiates a mod list when a client connects. 'Mod rejections' means the client is missing required mods, has extra ones, or runs different versions than the server expects, so the handshake fails. The disconnect details which mods were rejected. 
Connection closed - mod rejections [...]
Most Common Causes
  • The client is missing mods the server requires.
  • The client has extra mods the server does not.
  • Different versions of the same mod on each side.
  • Client-only mods not marked as such, so the server rejects them.
  • An out-of-sync modpack between server and players.
How To Diagnose
  1. Read the rejection list, it names the offending mods.
  2. Compare the client and server mods folders.
  3. Confirm both run identical mod versions.
  4. Identify any client-only mods that should be ignored in the handshake.
Recommended Fixes
  • Sync the modpack
    Install the exact same mods and versions on client and server.
  • Match versions
    Replace mismatched mod versions so both sides agree.
  • Handle client-only mods
    Keep purely client-side mods off the server, and ensure they are not required by the handshake.
  • Distribute the pack
    Share the modpack/zip so every player runs the identical set.
Analyze My Log
Frequently Asked Questions

The disconnect screen lists the rejected mods, that tells you what to add, remove, or align.

They can if not handled correctly. Keep them off the server and ensure they are not part of the required handshake set.

Distribute the modpack as a single package so all clients match the server exactly.