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, 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:

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


  def allow_optimizely_editor
    response.headers['X-Frame-Options'] = 'ALLOW-FROM'

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.

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