From November 1, 2019, when publishing updates to Google Play applications, they must support API Level 28, which are designed for Android 9 Pie. A similar rule, but for publication in the store of new programs, valid from August 1.
In this way, Google encourages application developers to keep up with the latest platform changes, including those related to security and privacy. Such a requirement was announced in 2017.
For applications, there is still no lower bound for Android version support, i.e. programs can still work even with Android 1.0.
According to Google, at the end of August 2019, Android 9 Pie was installed on 22.6% of all certified Google Play devices.