Fenced frames - Send "Referer" header in beacons

concepts

1. Fenced Referer

   Fenced frame automatic beacons send a Referer header, matching iframe semantics. Cleaner attribution pipelines.

2. beacon types matrix

   Four ways a fenced frame fires a reporting beacon. v132 lights up the Referer header on three. Inspect the exact request the browser sends.

3. Referer-Policy explorer

   Same beacon, different Referrer-Policy headers. Pick a policy + destination protocol; see exactly which Referer flows.

4. attribution pipeline

   Four-step ad-tech pipeline. Toggle pre-v132 vs Chrome 132 and watch which fields the impressions table can populate.

why it shipped

Reporting beacons (for FenceEvent-built destination enum events, FenceEvent-built automatic beacon events, and macro-substituted destination URL events) will have their "Referer" header set to the initiating frame's origin. This is a strictly additive change, as the "Referer" header is currently unpopulated for all fenced frame event-level reports.

references

• ChromeStatus entry
• Spec