Configure your Rails application to use Optimizely

Thursday 2 April 2015

I just spent a couple of hours trying to have a rails app in the Optimizely Editor looks good, but the CSS and images were not showing up. Apparently, if Optimizely cannot load your website in the editor iframe, it uses a proxy, www.optimizelyedit.com to load the HTML. Fine. A rails application uses helpers (stylesheet_link_tag and image_tag) for CSS ang images which generate relative links. So basically it tried to download the CSS here:

https://www.optimizelyedit.com/assets/application-261102d8007ae1fff68a817ec78c9d94.css

Of course it does not exist…

By default, Rails is secure and prevents other website to load yours in an iframe. It’s done with the following HTTP header:

X-Frame-Options: SAMEORIGIN

You can override this behavior to allow Optimizely to load your site, and just them.

# app/controllers/application_controller
class ApplicationController < ActionController::Base

  after_action :allow_optimizely_editor

  private

  def allow_optimizely_editor
    response.headers['X-Frame-Options'] = 'ALLOW-FROM https://www.optimizely.com'
  end
end

That’s it! The Optimizely editor should now work. Oh, and of course, use ngrok to expose your port 3000 on the Internet and run Optimizely experiment on your development environment.