Change effective on 22 September 2016
Heroku SSL is free for custom domains on Hobby dynos and above and relies on the SNI (“Server Name Indication”) extension which is now supported by the vast majority of browsers and client libraries.
Note that our previous add-on, SSL Endpoint, will continue to exist. However, we highly recommend that you switch to Heroku SSL as we will be rolling out exciting new features to it over the coming months. In case you currently have an SSL Endpoint and would like to switch, we have some guidelines here on how to migrate from SSL Endpoint to Heroku SSL.
For more information, please see this Dev Center article.