It appears that passkeys are now supported for Apple IDs, but only if you have the first beta for iOS 17 (or iPadOS 17 or macOS Sonoma). Beta users of Apple’s operating systems then have the ability to sign in anywhere that supports signing in with your Apple ID — covering not only Apple.com and icloud.com, but also anywhere else your Apple account is linked to — sans passwords, using just the biometrics on their iPhone or MacBook and a dream.
It works anywhere that supports signing in with your Apple ID. For example, if I want to sign in to Reddit and look at my favorite John Oliver-themed subreddits, I can tap the “Continue with Apple” button on the sign-in screen, and I’ll be given the option to sign in by scanning a QR code with my iPhone.
The feature appears to work on any Apple device — I was able to use a passkey successfully in Chrome, Safari, and Arc. When trying on a Windows PC in Chrome, the same “Sign in with iPhone” button showed up, but the request timed out when I scanned the QR code. On an Android phone, I didn’t see the button at all.
Once you’ve created the passkey on your iPhone, iPad, or Mac, it syncs across all of your Apple devices, letting any of them use the biometric logins set up on that system to sign in with your Apple ID. Since passkeys aren’t exclusively the domain of Apple, once it’s fully launched, you should be able to generate them on non-Apple devices for passwordless sign-in with your Apple ID, too, using Android or Windows using either the Chrome or Edge browser, which each support passkeys.
https://www.theverge.com/2023/6/20/23767583/apple-iphone-ios-17-beta-passkey