Heroku-20 is now the default stack for new apps

Change effective on 13 January 2021

Heroku-20, our stack based on Ubuntu 20.04 Long Term Support, is now the default stack when creating new applications.

See the Heroku-20 stack article for a list of changes over the previous default stack, Heroku-18.

To continue creating new apps using Heroku-18, specify the stack explicitly when creating the app:

$ heroku create --stack heroku-18

If you use Review Apps or Heroku CI, the default stack can be overridden by defining a stack in app.json:

   "stack": "heroku-18"

Existing apps are unaffected by this change in default stack. To upgrade them to Heroku-20, see upgrading to the latest stack.