Back in October 2014 i had an interesting project. My task was to build a canvas facebook app for an existing web app called wishlist. My first thought was, how hard could it be? You just do what you do every day, coding a rails app. It could be very hard. I had some struggles with the sign in process and third party cookies. I want to tell you about it in this post. But first what is a canvas facebook app? A canvas app is an app who runs in facebook as an iframe. Not really 2015, i know, but iframes are not dead, yet, unfortunately.