Protected Audience API: The alternative remarketing solution to third-party cookies



October 4, 2023

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Better Ads Standards compliant
💡 We summarized everything publishers, advertisers, and marketers need to know about Google Chrome’s Protected Audience API in a 2-minute guide.

After multiple delays over numerous years, Google has once more updated the timeline for phasing out third-party cookies in Chrome. The gradual phase-out will begin midway through next year, in 2024. The disappearance of third-party cookies is inevitable, and the digital advertising world has been preparing accordingly. To fulfill advertiser and publisher needs in a cookieless era, Google is developing a remarketing tool called the Protected Audience API. Let’s take a closer look.

What is the Protected Audience API?

The Protected Audience API (formerly known as FLEDGE) is a part of Google’s Privacy Sandbox technology. Privacy Sandbox technology enables remarketing and custom audience use cases without third parties tracking user browsing behavior across sites. The Protected Audience API facilitates on-device ad auctions hosted by the browser. Like third-party cookie retargeting, this technology displays relevant ads to users based on browsing history. However, by hosting on the browser level, the user’s information does not need to be shared with various third parties across ad networks. This allows for a device-centric, privacy-centric approach to programmatic advertising.

An overview of each stage of the Protected Audience API lifecycle

To understand how the Protected Audience API works, let's go through an example scenario. Say a user visits a website selling bikes. Ad space buyers (either the bike website itself or a DSP) will ask the user’s browser to join an ad interest group for bikes. This will also indicate the user's interest in the specific visited bike website. When the user visits other websites with ad displays, their browser will host auctions selling the website's ad space (the sellers being either an SSP or the site itself). Most importantly, the bidding for filling ad inventory will be based on the user's interest group memberships. In other words, the bidding ads will be relevant to the user's browsing history - in this case, bike sales. The user in this scenario will continue to see bike ads, potentially including ads from the specific visited bike website. Thanks to the Protected Audience API’s in-browser auctions, ads are retargeted to users without ad buyers and sellers accessing the user's browsing history.

How to try the Protected Audience API

An experimental version of the Protected Audience API, dubbed the Privacy Sandbox Relevance and Measurement origin trial, just closed recently (September 20, 2023). Many ad-tech companies, including Ad-Shield, had participated in the trial early on. If you missed the trial but still want to test the API, no worries: the API is currently available for 99% of Chrome users. Google has shared various resources for trying out the now (mostly) live API.

First, check out the Protected Audience API Developer Guide to learn about the methods and parameters.

Second, try the demo. If you need extra help, review the source code or watch the demo video. (Tip: Watch at an increased playback speed to save time.)

Finally, experiment with the actual API. Try it out for a single user by enabling chrome://flags/#privacy-sandbox-ads-apis . Alternatively, you can run Chrome from the command line with Protected Audience feature flags

David Jeon
Lead Software Engineer