Firebase - How to check whether a user has already signed up using Phone Number

Question

I am using firebase phone Authentication . When a user creates a account using phone number and next time he creates account with same phone number Than I want to show a m

Answer 1

For the solution,

After signup please make some entry in Database which makes an identity of the user, so next time you can identify user already signup.

After OTP verification check in RealTime database already Mobile number exists then so its already otherwise do an entry of that particular mobile number.