Google Analytics for Firebase, also called Firebase Analytics, is an app measurement service from Google. It records how people use a mobile or web app and turns those records into reports. It is part of Firebase, Google's platform of hosted services for building and running apps.
A developer adds the Firebase SDK (software development kit, a library built into the app) for iOS, Android, the web, Flutter, Unity or C++. The SDK captures some events and user properties automatically, and the developer can define custom events. Reports cover up to 500 distinct events and appear in a dashboard in the Firebase console, from active users and demographics to the most purchased items. Custom audiences built from events and user properties can target notifications, A/B tests and Google Ads campaigns. Realtime views show live use, and the raw event data can be exported to BigQuery, Google's data warehouse, for custom analysis.
It is a hosted Google service, and Google charges nothing for its use.