Can someone explain to me what "Sign in with Apple" is?

[ian87w]

Well, I kinda have an idea what it is, but I just cannot seem to understand how it is implemented. Correct me if I'm wrong, but the idea is similar to Sign in with Google/Facebook/etc, right? But it's more privacy focused.

My questions:
1. I have used Sign in with Google for many things. Does this Sign in with Apple means I have to create a new account with each of those websites/services? That would be annoying and would prevent me form using it.
2. I tried Sign in with Apple on a website (forgot what it was though), and it didn't work. The website still ask for the same registration requirement like email and a password. So how is this useful?

 

[Apple_Robert]

What is Sign in with Apple? - Apple Support

With Sign in with Apple, you can privately sign in to participating third-party apps and websites using your Apple ID.

support.apple.com

Sign In With Apple - Supported Apps & Sites

I still cannot see any SIWA in my Reddit app.

forums.macrumors.com

 

[ian87w]

What is Sign in with Apple? - Apple Support

With Sign in with Apple, you can privately sign in to participating third-party apps and websites using your Apple ID.

support.apple.com

Sign In With Apple - Supported Apps & Sites

I still cannot see any SIWA in my Reddit app.

forums.macrumors.com

If I already have an existing account on the service/website, what then? Do I have to get a new account if I use sign in with Apple?

 

[KALLT]

That depends on the website/app. Some let you add Sign In With Apple access to your existing account. You’d usually find this in the account settings.