[mooreds]

What is the win of this over webauthn (if the website supports it)? I guess the big win is that the graceful fallback is smoother.

Seems like a lot of moving pieces that only an OS vendor (who controls both the browser and the email client and could build the integration between them) could implement.

[adrr]

Webauth authenticates the device. Still need a way to authenticate the user then you can use webauth going forward on the device. This is assuming you’re using the TPM chip on the device and another FIDO2 device. Standard user won’t have a FIDO2 device like a yubikey but if their phone or computer is relatively new, they will have a TPM chip.