If you have already enabled two-step authentication via SMS, a mobile app, or a hardware security key, you have the additional option of adding one or more Touch ID-capable devices, such as a 2017 or newer MacBook Pro and a 2018 or newer MacBook Air. When signing in from these devices, you can use Touch ID instead of SMS, an authenticator app, or a hardware security key to complete two-step authentication.
You will not be able to use Touch ID when signing in from a device that was not added to your account. In these cases, you will need to use SMS, your authenticator app, or a hardware security key to sign in.
The next time you sign in, you will be prompted to use Touch ID for two-step authentication. If you have a hardware security key, you can still use it while being prompted for Touch ID. You can also cancel and opt to use a verification code instead, either through SMS or a mobile app.
Touch ID is supported through WebAuthn, which requires a modern browser.