v133 · network / connectivity

Storage Access Headers

Offers an alternate way for authenticated embeds to opt in for unpartitioned cookies. These headers indicate whether unpartitioned cookies are (or can be) included in a given network request, and allow servers to activate 'storage-access' permissions they have already been granted. Giving an alternative way to activate the 'storage-access' permission allows

concepts

  1. Storage Access Headers

    HTTP request/response headers for the Storage Access API. Top-frame and third-party servers can coordinate access without script.

  2. Header flow explainer

    Side-by-side comparison of the JS Storage Access API round-trips vs the new header-driven single-round-trip flow, with a live fetch probe.

  3. Policy designer

    Pick top-frame permission, third-party intent, credentials mode, and response activation; the page generates the header pair and predicts the cookie verdict.

  4. Round-trip comparison

    Animate both the JS Storage Access API flow (3–4 round trips) and the new header-based flow (1 round trip) side-by-side with configurable per-hop latency. Shows total time saved and why headers work for non-iframe subresources.

why it shipped

The Storage Access API currently supports authenticated embeds’ ability to opt in for unpartitioned cookies by requiring them to call into a JavaScript API. This creates latency as the process undergoes multiple network round trips, and it limits use cases by requiring the embedded resources to use an iframe.

references