Understanding SSL on Heroku
Last updated January 07, 2023
There are two ways to enable SSL for your Heroku app’s custom domains (listed in order of recommended use):
- Automated Certificate Management (ACM)
- Heroku SSL
In general, your app should use Automated Certificate Management unless it requires functionality that ACM does not support. Summaries for the functionality provided by each method are provided below.
For enabling SSL on apps in Private Spaces, please refer to the documentation here.
SSL is always enabled for
.herokuapp.com for Common Runtime apps.
When to use Automated Certificate Management (ACM)
With Automated Certificate Management (ACM), Heroku automatically manages TLS certificates for apps running on paid dynos on the Common Runtime. Certificates handled by ACM automatically renew one month before they expire, and new certificates are created automatically whenever you add or remove a custom domain.
ACM is recommended for most Heroku apps, because:
- It provides TLS certificates at no additional cost
- It supports creating certificates for multiple domains
- It automatically renews TLS certificates before they expire
ACM does not provide support for:
- Wildcard domains
- OV/EV certificates
- Apps using internal routing
- Eco dyno apps
If your app requires any of the functionality that ACM doesn’t support, it should use Heroku SSL instead.
DNS Targets for ACM
DNS targets for ACM will end with
herokudns.com for Common Runtime apps, or
herokuspace.com for Private Spaces apps e.g.
example.com example.com.herokudns.com www.example.com www.example.com.herokudns.com
or for Private Spaces
Again, wildcard domains are not supported by ACM.
When to use Heroku SSL
Heroku SSL is a free service for apps running on paid dynos that allows you to upload your own TLS certificate. You are responsible for purchasing and renewing this certificate.
Use Heroku SSL instead of Automated Certificate Management (ACM) if:
- You want to use an OV/EV certificate
- Your app needs to support wildcard domains
- Your app uses internal routing
Heroku SSL uses Server Name Indication (SNI), an extension of the TLS protocol.
DNS Targets for Heroku SSL
DNS targets for Heroku SSL follow these patterns:
example.com example.com.herokudns.com www.example.com www.example.com.herokudns.com *.example.com wildcard.example.com.herokudns.com