Sign in with Apple was first announced at WWDC 2019 with iOS and iPadOS 13. When you use Sign in with Apple on an app, Apple automatically fills out your information, and can even choose a random email address to register on the app which will forward all mails from that unique & random email address to your personal email address. If you see that the app is sending unnecessary and spam emails, you can easily turn the unique & random email address off. This way, you can be registered to apps & services without revealing your personal email ID. Users can authenticate with Face iD/Touch ID to Sign in with Apple. It’s that simple!
The deadline for apps to implement Sign in with Apple was recently extended from April 30th 2020 to June 30th 2020. Regardless of this extension, few Apps like The New York Times, Medium, IFTTT, Ritual, Strava, Freshii, Dozens and Fiverr have already implemented Sign in With Apple ahead of the deadline provided to them which is on June 30th 2020. If you do not see the option to Sign in with Apple, it will be rolled out soon to users gradually.
MacRumors Forum member has listed many apps which implemented this feature:
Apple users, it’s been a big week for Sign In With Apple. Apps like Medium, IFTTT, NYTimes, Strava, Ritual, Freshii, Fiverr and dozens more now offering the privacy of Apple’s anonymous sign in method. I was able to drop Facebook logins entirely. No more tracking me Zuckerberg!
— @iPedro on Post // ? (@MetroManTO) April 5, 2020