Deploying Phoenix to Heroku using CloudFlare

I started developing my personal blog (and a basic CMS) using Phoenix.

I successfully deployed it to Heroku following the Documentation/Guides, it’s live.

Now I added my custom domain “” to the Heroku App but everytime I access it, the URL on the browser switches from that custom domain to the “Heroku app URL” (

Am I missing something?

It might be useful to know that the DNS is being managed by CloudFlare, using CNAME flattening as recommended by CloudFlare itself.


Looks like everything on the Phoenix end is ok, but your domain settings are incomplete - did you follow the full instructions here:

Sure enough, the issue was within config/prod.exs.

I had hard coded the Heroku URL there in order to take advantage of Heroku’s free SSL when using their subdomains.

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@jaysoifer To solve this did you just change to in config/prod.exs and left everything else the same?

It’s been a while and I eventually gave up on this project sorry. I do clearly remember that is not what I did at that time…