Apps can now have multiple TLS certificates

Change effective on 22 March 2021

Previously, an app on Heroku could only have one TLS termination certificate. Over the past couple of months we have been relaxing this constraint, starting with certificates generated with Heroku ACM. As of today all apps on the platform can use multiple certificates, whether as part of ACM or manually uploaded.

See the Dev Center articles on SSL and Custom Domains for details on how to map certificates to domains.