Official Description: AndroidX Ads Identifier

CommonsWare’s Notes

This appears to be an abstraction around advertising IDs, with a pluggable provider system.

The main entry point seems to be AdvertisingIdClient, which has an isAdvertisingIdProviderAvailable() static method to tell you if a provider is available and a getAdvertisingIdInfo() static method to get an AdvertisingIdInfo that contains the actual ID.