Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The FencedFrameConfig interface represents the navigation of a <fencedframe>, i.e. what content will be displayed in it.

FencedFrameConfig objects cannot be constructed manually via JavaScript. They are returned from a source such as the Protected Audience API and set as the value of HTMLFencedFrameElement.config.

A FencedFrameConfig object instance has an exposed method, but it also maps to internal config information containing opaque properties not accessible from JavaScript. This includes information such as the source of the loaded content and interest groups for advertising purposes. It is key to how fenced frames help to implement key use cases while respecting user privacy.

Instance methods

setSharedStorageContext() Experimental

Passes in data from the embedding document to the <fencedframe>'s shared storage.


Basic usage

To set what content will be shown in a <fencedframe>, a utilizing API (such as Protected Audience or Shared Storage) generates a FencedFrameConfig object, which is then set as the value of the <fencedframe>'s config property.

The following example gets a FencedFrameConfig from a Protected Audience API's ad auction, which is then used to display the winning ad in a <fencedframe>:

const frameConfig = await navigator.runAdAuction({
  // ...auction configuration
  resolveToConfig: true,

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

Note: resolveToConfig: true must be passed in to the runAdAuction() call to obtain a FencedFrameConfig object. If it is not set, the resulting Promise will resolve to a URN that can only be used in an <iframe>.

Passing contextual data via setSharedStorageContext()

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

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: {

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;

      bucket: convertEventIdToBucket(eventId),
      value: convertEventPayloadToValue(eventPayload)

register('send-report', ReportingOperation);


Fenced Frame
# fenced-frame-config-interface

Browser compatibility

BCD tables only load in the browser

See also