Handling ActionController::UnknownFormat

application_controller.rb

class ApplicationController < ActionController::Base
  
  # Rather than return a 500 (internal server error) let's just say we can't
  # find what they are looking for. Typically, this is when someone hits one
  # of our valid routes but asks for the .xml format or something. 
  rescue_from ActionController::UnknownFormat, with: :raise_unknown_format

  def raise_unknown_format
    render plain: 'Unknown Format', status: :not_found
  end
  
  ...
    
end