Is it possible to check phone number is already registered in firebase else goto sign up

Question

Is there anyway to check entered mobile number in login activity is already registered with firebase before generating OTP? If not registered, I want to goto signup activity

Answer 1

Here is one solution:

You can write a Cloud function and add each phone number to Cloud Firestore while using Phone Authentication and then you can easily call the function from your app and check whether it is registered or not.

Visit https://firebase.google.com/docs/functions/callable