Firebase Authentication Google vs Facebook vs Email pros and cons

Question

I am a newbie to Firebase authentication, please pardon my ignorance.

I am thinking of the pros and cons of adding different types of authentications to my app, instead of adding only one (Google).

Adding all 3 (Google, Facebook and Email) would be more considerate of the user and their email preferences. That's the only reason I can think of, that I would add all 3. Are there any other reasons, if all I need is a user Id, and a way to send the user emails?

What would be the reason to add Facebook if anyone who has an android app has a google account?

And why would I add email authentication? This might discourage the user to enter an email if they have to type it.

I hope this question does not get closed. I am not looking for opinions. I am looking for facts only.

Answer 1

If you are really looking for facts, then i'd suggest Google authentication via Email Auth. But why?

Like you said;

What would be the reason to add Facebook if anyone who has an android app has a google account?

I've personally seen some users don't even care to sign in on their Google account. Meanwhile, there are users who's really working with Google Play Store and they care!

So, adding Google authentication via Email Auth will be a good choice for those who's already signed in and they can logged in very quickly and simply by clicking on Google Sign in Button and also, Email Auth for those who's not signed in by Google and love to give the app a shot by their Email.

Adding FaceBook or other Authorization method will be a good choice to use on IOS. But why? Because in IOS there is an Apple Id which you can't use it for signing in on applications like Google. Not sure, i'm not an IOS developer but i don't think Apple would allow such a thing so, those two will be enough for users on Android Platform because Google made it easier to use one account which can be logged in on applications by a Button.

Also, nowadays, the best option to develop application or in whatever in our life, is to make something which makes human work quick & easily like Kotlin or this Signed in Button which those really are a life and time saver. :)