Currently Firefox for iOS does not support third party key boards. I also tested it and did not see Swiftkey come up in the webpage entry or in the url bar. However I did learn how to go a google search with smileys.... What I would recommend it to submit this feedback to the iOS team: We're always looking for ways to improve Firefox for iOS. Please visit this page to submit your request where our engineers can review it. Thank you for giving Firefox for iOS a try!