CORS development.rb

development.rb

 config.middleware.insert_before 0, "Rack::Cors", :debug => true, :logger => (-> { Rails.logger }) do
    allow do
      origins '*'

      resource '/cors',
               :headers => :any,
               :methods => [:post],
               :credentials => true,
               :max_age => 0

      resource '*',
               :headers => :any,
               :methods => [:get, :post, :delete, :put, :options, :head],
               :max_age => 0
    end
  end

This allows two apps running in development to access the same domain from a different subdomain (shop.archer.dev -> client.archer.dev)