Automated Certificate Management
Last updated 12 September 2017
Table of Contents
With Automated Certificate Management (ACM), Heroku automatically manages TLS certificates for all apps that have Hobby and Professional 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. All applications with paid dynos include ACM for free.
Automated Certificate Management uses Let’s Encrypt, the free, automated, and open certificate authority for managing your application’s TLS certificates. Let’s Encrypt is run for the public benefit by the Internet Research Security Group (ISRG).
Setup
Enable Automated Certificate Management
ACM is enabled by default for all applications created after March 21, 2017 that are running on Hobby or Professional dynos. The following steps are for applications currently running on Free dynos, and for applications created before that date.
If your app is currently running on Free dynos, Automated Certificate Management is enabled automatically when you upgrade your app to use Hobby or Professional dynos:
$ heroku ps:resize web=hobby
If your app is already running on Hobby or Professional dynos, you can enable ACM by running the following command:
$ heroku certs:auto:enable
When you enable this, you need to ensure your DNS is pointed at its new DNS target. If it’s pointed at *.herokuapp.com or *.herokussl.com, Heroku is unable to verify your certificate. Run heroku domains to verify the DNS target.
View your certificate status
It takes approximately 45 - 60 minutes to fully generate a TLS certificate for custom domains on your application. You can view the status of the certificate that is generated for all of your custom domains by running:
$ heroku certs:auto
If your status says “DNS Verified”, the process is not finished yet. It means we have verified your domain status and are still in the process of submitting it to Let’s Encrypt. The process will be complete when it says “OK”.
If your certificate is currently being generated, you may see different states next to the custom domains on your application.
| Status | Description |
|---|---|
| OK | Everything looks normal. |
| In Progress | Heroku is verifying all of your custom domain’s DNS. |
| DNS Verified | Heroku verified all of your custom domain’s DNS and is in the process of generating the certificate. |
| Waiting | Heroku is currently waiting to process your certificate. |
| Failing | Heroku is unable to verify your DNS. We will keep trying to verify for another hour. See Troubleshooting for help addressing this error. |
| Failed | Heroku is unable to verify your DNS. We have stopped trying to verify this domain. See Troubleshooting for help addressing this error. |
Providing your own TLS certificate
If you’d prefer to use a different type of TLS certificate, such as one from a different CA, a wildcard certificate, or an EV certificate, you can easily do so.
Simply upload your own certificate, following the steps listed in the Heroku SSL Dev Center article.
Providing your own certificate disables ACM for your application. If you want to re-enable ACM, you can run:
$ heroku certs:auto:enable
Turning off Automated Certificate Management
Do not turn ACM off with the intent of turning it immediately back on. This will instead cause your account to hit a rate limit with Let’s Encrypt.
You can easily turn Automated Certificate Management off by running:
$ heroku certs:auto:disable
This removes your domain’s certificate and turns off ACM for your application. Removing your certificate with heroku certs:remove also turns off ACM.
Migrating existing applications
Migrating from Heroku SSL with your own certificate
Automated Certificate Management uses the same DNS configuration as our existing Heroku SSL (SNI) support. Although it might take some time to verify your DNS configuration, your app will continue to serve your existing SSL certificate while verification is taking place. Your app should continue to remain available at your custom domain throughout the process.
Migrating from SSL Endpoint
Migrating from the SSL Endpoint addon to Automated Certificate Management requires a DNS change. However, you can use Heroku SSL (SNI) as an intermediate step to avoid downtime for your custom domain. Start by following these instructions to migrate from SSL Endpoint to Heroku SSL (SNI). Once that process is complete, you can enable ACM with no downtime as described above.
Troubleshooting
Do not turn ACM off and on in an attempt to fix or speed up the ACM process. This will instead cause your account to hit a rate limit with Let’s Encrypt.
Verification errors
If heroku certs:auto shows “Failing” or “Failed” for any domain when you run heroku certs:auto, it means Heroku was unable to verify DNS for a given domain. You need to verify that it is pointed to the correct DNS target as specified in heroku domains. The DNS targets will be in the format <your-domain.herokudns.com.
If your DNS is pointed at older DNS settings, such as *.herokuapp.com or *.herokussl.com, Heroku will not be able to generate a certificate.
If ACM is unable to create a certificate for your domain, you receive a notification after three days of attempts. In most cases, this error occurs because DNS is not properly configured for your domain. After you resolve your DNS issue, run the following command to instruct ACM to try again:
$ heroku certs:auto:refresh
Known limitations
- ACM does not support applications that have over 100 custom domains.
- ACM does not support applications that have wildcard custom domains.
- ACM does not support the SSL Endpoint add-on.
- ACM is currently available for apps on the Common Runtime only. It is not yet available in Private Spaces.
- ACM is not available if your app is behind a CDN such as Cloudflare or Fastly.
Alternatives
- If you want to automatically renew a wildcard certificate, or use a different CA, we recommend checking out providers in our ecosystem such as SSL FastTrack or ExpeditedSSL.