Heroku Reverse Proxy

Installing plugin will enable the middleware layer to enable this out of the box.

SSL certificate

If you are on a paid Heroku plan and would like to add SSL certificates to your website manually rather than using their Automated Certificate Management for some reason, then the Heroku plugin has additional provisions for enabling this. First install the plugin and deploy it to Heroku. Now visit the plugin's settings page and you will reach this:

You need to add the challenge keys here which can be generated using certbot tool. First ensure it's installed by using:

brew install certbot

Then manually fetch the certificate:

sudo certbot certonly --manual

It will ask for the domain names and you can add www.yourwebsite.com and yourwebsite.com

Now it will throw out a URL and a challenge key for each domain. Copy the slug part of the URL and paste it in the challenge slug field and the challenge key in the key field. Do this for each domain and save the settings. Now go back to command line and hit enter which will validate the keys. And that's it, you have the certificates installed. You can upload them using:

heroku plugins:install heroku-certs
heroku certs:add /etc/letsencrypt/live/yourwebsite.com/fullchain.pem /etc/letsencrypt/live/yourwebsite.com/privkey.pem

And if you are on a paid plan, it should work fine.