I am integrating my app with Firebase and I have added the ability for users to create accounts using their email, FaceBook, Google accounts.
My app is still under development and yet to be pushed to the app store. Its only available on iOS right now. However Firebase analytics reports that there are 38 active users when I am the only one actively building it.
Active users are the unique users who initiated sessions for a period of time. When you install, uninstall and install the app again, then that will be counted as two active users.
If you'd like to learn more about this Firebase dashboard metric, check out this Firebase help documentation.
As looptheloop88 correctly answered uninstalling and reinstalling the app is considered new active user. If your app provides IDFA you will also log the IDFA identifier. Linking your app to BigQuery will export the raw data to BigQuery table. You can then count the number of distinct IDFA values. That will give you the number of distinct devices your app was installed. Please note that IDFA can be reset by the user so the distinct IDFA is not exactly the number of distinct devices but will be reasonable close.
