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Introducing Initial OpenRTB Support for the Protected Audience API

Google’s Privacy Sandbox introduces a number of APIs that impact how advertising is bought and sold. Some of them, like TOPICS, are relatively straightforward and were successfully mapped to existing programmatic constructs. Others, like the Protected Audience API, are significantly more complex and require the evolution of OpenRTB for clear and effective support.

Now: Connecting the Pipes

As the IAB Tech Lab website states, the goal of OpenRTB is “to spur growth in RTB marketplaces by providing an open industry standard for communication and interoperability between buyers and sellers.” In this regard it has been incredibly successful. Not only is it the lingua franca for server-side real-time bidding, it is becoming the standard used by SSPs for their own APIs as well as core to header bidding in Prebid.js and Prebid Server. Maintaining this success requires evolving with the ad-tech ecosystem, which in this case means standardizing support for the Protected Audience Auction. 

The Protected Audience API is, at its core, a new form of real-time bidding that takes place in the browser. Due to restrictions on information flow imposed by the Protected Audience API, the browser RTB interaction must take place following the server-side RTB interaction. Additionally, the server-side RTB interaction can serve as a conduit for information that flows into the Protected Audience Auction. In this release OpenRTB is introducing multiple signals as community extensions, including the new igs attribute (of type InterestGroupAuctionSupport) in the Imp object to enable sellers to communicate the availability of the Protected Audience Auction. OpenRTB is also introducing the igi attribute (of type InterestGroupAuctionIntent)in the BidResponse object so buyers can register their intent to participate in the Protected Audience Auction. These, in addition to two other new objects, enable buyers and sellers to begin connecting the Protected Audience pipes to the existing real-time bidding pipeline.

This work is the result of the Privacy Sandbox in OpenRTB, a subgroup of Programmatic Supply Chain, chaired by Hillary Slattery with contributions from representatives of many SSPs and DSPs. Many thanks to David Dabbs of Epsilon, Isaac Foster of Microsoft, Roni Gordon of Index, and many others for their work to quickly address this need.

Next: Enabling a New Context

While the Protected Audience API provides the javascript API for creating browser-based audiences, bidding on them, and evaluating those bids, it doesn’t specify the level of information needed for successful “communication and interoperability between buyers and sellers.” As noted above, the Protected Audience Auction is effectively a new form of real-time bidding. Thankfully OpenRTB has already standardized the concepts that are necessary for a buyer and seller to transact, even in the browser. In the next few months the Sandbox in OpenRTB subgroup will be focused on identifying the right way to leverage OpenRTB within the Protected Audience Auction Context, particularly as it relates to communicating metadata about the seller’s context and restrictions, and the buyer’s bid and creative asset.

Future: A Multi-Context World

Over time OpenRTB evolved to support a variety of formats as the scope of programmatic advertising grew. Now we’re seeing OpenRTB evolve to support an entirely new context: a proprietary in-browser real time auction. Not all attributes make sense in every context. For example, the newly introduced igs and igi attributes and associated objects don’t apply within the Protected Audience Auction context – they are only applicable in the existing programmatic/contextual context leading up to it. While the majority of OpenRTB will be relevant in every context, over time there are attributes that will be added that only make sense in one or another context. Setting the standard up for success means identifying and clearly explaining which attributes are context specific.

It’s exciting to reflect on the success of OpenRTB and the way it has enabled programmatic advertising to succeed. It’s also exciting to think about the future and how we can architect the standard for continued growth and even greater impact in the future.


Joel Meyer
SVP, Engineering
Open X