FencedFrameConfig: setSharedStorageContext() method

context

A string representing the contextual data to pass in to shared storage. Once set, this will be stored in the internal config storageContext property.

None (Undefined).

You can use the Private Aggregation API to create reports that combine event-level data inside fenced frames with contextual data from the embedding document. setSharedStorageContext() can be used to pass contextual data from the embedder to shared storage worklets initiated by the Protected Audience API.

In the following example, we store data from both the embedding page and the fenced frame in shared storage.

In the embedding page, we will set a mock event ID as the shared storage context using setSharedStorageContext():

const frameConfig = await navigator.runAdAuction({ resolveToConfig: true });

// Data from the embedder that you want to pass to the shared storage worklet
frameConfig.setSharedStorageContext("some-event-id");

const frame = document.createElement("fencedframe");
frame.config = frameConfig;

Inside the fenced frame, we add the worklet module with window.sharedStorage.worklet.addModule(), and then send the event-level data into the shared storage worklet using window.sharedStorage.run() (this is unrelated to the contextual data from the embedding document):

const frameData = {
  // Data available only inside the fenced frame
};

await window.sharedStorage.worklet.addModule("reporting-worklet.js");

await window.sharedStorage.run("send-report", {
  data: {
    frameData,
  },
});

In the reporting-worklet.js worklet, we read the embedding document's event ID from sharedStorage.context and the frame's event-level data from the data object, then report them through Private Aggregation:

class ReportingOperation {
  convertEventIdToBucket(eventId) { ... }
  convertEventPayloadToValue(info) { ... }

  async run(data) {
    // Data from the embedder
    const eventId = sharedStorage.context;

    // Data from the fenced frame
    const eventPayload = data.frameData;

    privateAggregation.sendHistogramReport({
      bucket: convertEventIdToBucket(eventId),
      value: convertEventPayloadToValue(eventPayload)
    });
  }
}

register('send-report', ReportingOperation);

• Fenced frames on developer.chrome.com
• The Privacy Sandbox on developer.chrome.com