Mandatory so long as the app supports other third party authentication. If they exclusively use only their own accounts, it isn't required. (There are a couple

Mandatory so long as the app supports other third party authentication. If they exclusively use only their own accounts, it isn't required. (There are a couple other exceptions for business and education apps) Edit: https://developer.apple.com/news/?id=09122019b https://developer.apple.com/news/?id=09122019b New Apps will be required to implement this immediately, existing apps have until April next year to support it before updates will be rejected.