A fingerprint security key and Windows fingerprint sign-in are separate things.
A security key is a physical device used instead of a username and password, and it is unlocked with a fingerprint or PIN on the key itself. That means the fingerprint can be stored and used by the security key, not necessarily by Windows.
For a personal Microsoft account, Windows provides this path to use a security key:
- Go to Start > Settings > Accounts > Sign-in options.
- Select Security Key.
- Select Manage and follow the instructions.
About the "Windows 10 1903 or later" wording:
- Windows support for FIDO2 security key sign-in and the best experience is documented for Windows 10 version 1903 or higher.
- Windows 11 is newer than that, so it meets that requirement.
About fingerprint registration on the home PC:
- Registering a fingerprint in Windows Hello is for Windows biometric sign-in on the PC.
- A fingerprint security key can use its own fingerprint or PIN to unlock the key.
- Those are not the same enrollment.
If the key manufacturer says to register a fingerprint in Windows, that can refer to Windows support for fingerprint-related experiences, but the provided guidance for security keys only shows setting up the Security Key option in Sign-in options and then following the device instructions.
If using a fingerprint scanner attached to the PC for Windows Hello, Windows can require a PIN first, and fingerprint is enrolled afterward. On supported devices, fingerprint enrollment is done through Settings > Accounts > Sign-in options.
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