v131 · miscellaneous

FedCM as a trust signal for the Storage Access API

Reconciles the FedCM and Storage Access APIs by making a prior FedCM grant a valid reason to automatically approve a storage access request.

concepts

  1. FedCM ↔ SAA

    FedCM sign-in counts as a trust signal when the embedded origin later asks for Storage Access. Smoother UX for federated-sign-in flows.

  2. Embedded iframe verdict simulator

    The motivating case: an embedded SSO widget. Pick the inputs (FedCM IdP? recent sign-in? prior grant?) and see whether the prompt auto-resolves.

  3. FedCM → SAA step-by-step

    Five-step flow visualisation: shop.com sign-in → IdP picker → token → iframe SAA → v131 auto-grant.

  4. Capability probe

    Every related API tile-by-tile: credentials.get, requestStorageAccess, IdentityCredential, partitioned cookies, secure context.

why it shipped

FedCM is an API that mediates federated user identity flows through the application of (ideally) well-understood, purpose-driven user interfaces. Using the navigator.credentials API, it exposes a high-entropy user identifier (token) from an IdP to an RP.

references