Automated Certificate Management (ACM) support for wildcard domains for Common Runtime apps

Change effective on 30 September 2024

Heroku’s Automated Certificate Management (ACM) feature now supports wildcard domains for apps in the Common Runtime. Previously, apps with wildcard domains must manually add their own certificate. Now, Common Runtime apps with wildcard domains can use ACM for managing TLS certificates.

Note that if you have both a certificate for a wildcard domain and a specific domain for your app, the specific domain’s certificate takes precedence over the wildcard certificate. Removing the specific domain’s certificate results in the app defaulting back to the wildcard certificate. See the ACM article for more info.