Report on Protected Audience API auction results

Seller and buyer guide to generate Protected Audience API auction reports.

This article is a technical reference for generating reports for Protected Audience API auction wins, as used in the current iteration of the experimental Protected Audience API.

Read the developer guide for the full life cycle of the Protected Audience API, and refer to the Protected Audience API explainer for an in-depth discussion of event-level reporting (temporary).

Not a developer? Refer to the Protected Audience API API overview.

What does the Protected Audience API report?

There are two available Protected Audience API reports:

  • Seller report: Informs the seller of the ad auction winner.
  • Buyer report: Available to winning buyers only, to learn that they've won an auction.

The long-term plan is to allow the browser to report auction results for the seller and buyers with the Private Aggregation API APIs. As a temporary event-level reporting mechanism, the code implementing reportResult() for the seller, and reportWin() for the winning bidder, can call the sendReportTo() function. This takes a single argument: a string representing a URL that is fetched after the auction completes, which encodes event-level information to be reported.

API functions

Seller: reportResult()

The seller's JavaScript provided in decisionLogicUrl (which also provides scoreAd()) can include a reportResult() function, to report the auction outcome.

reportResult(auctionConfig, browserSignals) {
  return signalsForWinner;

The arguments passed to this function are:


The auction configuration object passed to navigator.runAdAuction().


An object constructed by the browser providing information about the auction. For example:

    'topWindowHostname': 'publisher.example',
    'interestGroupOwner': 'https://dsp.example',
    'renderUrl': 'https://cdn.example/url-of-winning-creative.wbn',
    'bid': <bidValue>,
    'desirability': <winningAdScore>

The return value of this function is used as the sellerSignals argument for the winning bidder's reportWin() function.

Buyer: reportWin()

The winning bidder's JavaScript (which also provided generateBid()) can include a reportWin() function to report the auction outcome.

reportWin(auctionSignals, perBuyerSignals, sellerSignals, browserSignals) {

The arguments passed to this function are:

auctionSignals and perBuyerSignals

The same values passed to generateBid() for the winning bidder.


The return value of reportResult(), which gives the seller an opportunity to pass information to the buyer.


An object constructed by the browser providing information about the auction. For example:

  'topWindowHostname': 'publisher.example',
  'seller': 'https://ssp.example',
  'interestGroupOwner': 'https://dsp.example',
  'interestGroupName': 'custom-bikes',
  'renderUrl': 'https://cdn.example/winning-creative.wbn',
  'bid': <bidValue>

Temporary reporting implementation

There are two methods available temporarily in Chrome for auction reporting:

  • forDebuggingOnly.reportAdAuctionLoss()
  • forDebuggingOnly.reportAdAuctionWin()

These methods each take a single argument: a URL to fetch after the auction is completed. They can be called multiple times, in both scoreAd() and generateBid(), with different URL arguments.

Chrome only sends debug loss/win reports when an auction runs to completion. If an auction is canceled (for example, due to a new navigation) no reports will be generated.

These methods are available by default in Chrome when you enable all the Ad privacy APIs under chrome://settings/adPrivacy. If you're running Chrome with command line flags to enable the Protected Audience API, you'll need to explicitly enable the methods by including the BiddingAndScoringDebugReportingAPI flag. If the flag is not enabled, the methods will still be available but do nothing.

All Protected Audience API API references

API reference guides are available:

The Protected Audience API explainer also provides detail about feature support and constraints.

What's next?

We want to engage in conversations with you to ensure we build an API that works for everyone.

Discuss the API

Like other Privacy Sandbox APIs, this API is documented and discussed publicly.

Experiment with the API

You can experiment and participate in conversation about the Protected Audience API.