Google Analytics (GA) sets a client ID for the app, based on one specific instance or installation. Please also see:
https://developers.google.com/analytics/devguides/collection/protocol/v1/parameters#cid
Below scenarios are true:
- User has multiple devices with the app installed = multiple client IDs = multiple users are measured in GA for this particular user.
- User removes and re-installs the app = new client ID = multiple users are measured in GA for this particular user.
But what if someone updates the app to a new version. Does GA calculate this as a re-installation?
I think your app will be removed quickly (so it looks like on your smartphone, since the app dissapears for a moment) and the new version will be restored.
Also, if your client ID is kept somewhere, how does Google remember your client ID when doing an app update?