With the rapid adoption of passkeys (and the underlying WebAuthn protocol), authentication has become more secure and user-friendly for many users. One of the standout advancements of passkeys has been the integration of Conditional UI, often referred to as "passkey autofill" or Conditional Mediation (in the following, we stay with the term Conditional UI).
Despite its recent introduction and ongoing adoption by browsers, there’s a noticeable gap in technical documentation and implementation advice for Conditional UI. This article aims to bridge that gap by explaining what Conditional UI is, how it works, and how to tackle common challenges during its implementation.