The FIDO2 specification defines all components that are required for the modern authentication procedure.
First and foremost is the repeatedly mentioned W3C standard WebAuthn, which allows online services to enable FIDO authentication via a standard Web API (written in JavaScript) that is also implemented in various browsers and operating systems. Applications that already support the standard declared in March 2019 include Windows, Android, and iOS (version 13 or higher) as well as the following browsers: Google Chrome, Mozilla Firefox, Microsoft Edge, and Apple Safari (version 13 or higher).
The second critical component is the Client to Authenticator Protocol (CTAP). This protocol enables the various FIDO2 tokens to interact with the browsers and also to act as authenticators. Both the browser used, and the desired hardware token must therefore be able to communicate via CTAP in order to use this security feature (including password-free login).