In the following steps replace:
- subdomainwith your desired subdomain.
- domain.comwith your domain.
- random.herokudns.comwith your Heroku DNS target (see step 1).
- In the Heroku deployment settings, under domains, click “Add domain”. Enter subdomain.domain.comto receive therandom.herokudns.comHeroku DNS target.
- In the Heroku deployment settings, under SSL certificates, ensure a certificate is automatically managed. If you don’t do this, attempting to visit https://subdomain.domain.comin a browser will fail with an SSL error.