I am using FirebaseUI and Firebase authentication to authenticate users using phone number. During testing I saw that when I first used my phone number I was sent an OTP but after that I have uninstalled and installed my app many times but now it does not ask for OTP and just verifies the phone number and logs me in. So I would like to know how is firebaseUI/auth doing it. Is it linking android device Id to a phone number or saving it in shared preferences which is saved on cloud?
If this is not the case how is firebase UI/auth doing it ? . My app only has location permission.