Why is a Passkey on Keychain deleted if I reset Windows Hello?

When you reset Windows Hello, it can lead to the deletion of passkeys associated with your Microsoft account on devices that were using that authentication method. This is because Windows Hello is designed to manage credentials and authentication methods for Windows devices, and resetting it may remove any stored passkeys that were linked to that account.

Since you mentioned that you do not have any Windows devices, your concern about the passkey being copied onto a Windows device is unfounded. The passkey stored in your Apple iCloud Keychain should remain secure and unaffected by the actions taken on Windows Hello, as they operate independently.

If your passkey was removed from the Sign In Options list, you may need to re-register it or create a new one to continue using it for authentication. It's always a good practice to ensure that your passkeys are backed up or stored securely, especially after any changes to your authentication settings.

If you have further concerns about your account security, consider reviewing your account settings and enabling additional security measures, such as two-factor authentication.

References:

• Support for passkeys in Windows
• Sign in with a passkey (FIDO2) for your work or school account