Is there way to identify android/ios app user for sure without requesting him to signup with google/email/facebook?
I'd like to implement this: User downloads app from PlayMarket/AppStore, app identifies him somehow and sends data about this user to server. By "data about this user" i mean only the data gathered based on user's actions in app, like misc preferences and settings. If user will uninstall app and install it again to different device but with the same google account, he should be properly identified as the one who used the app before.