Ad Selection API

Ad Selection API is the complex of web browser features in Microsoft Edge, aimed at providing advertisers and publishers with an opportunity to deliver personalized ads to End Users in a privacy-preserving environment. 

What is the Ad Selection API? 

As a part of the privacy-focused functional ecosystem, the Ad Selection API doesn’t rely on cross-site tracking, including third-party cookies and other identifiers, while still ensuring End Users are shown the relevant advertising content on publishers’ digital properties in Microsoft Edge.

From the technical standpoint, the Ad Selection API adopts several privacy-centered staples, which include: 

  • Use of the Trusted Execution Environment (TEE), which ensures the security of End Users’ data, while handling the complex computational tasks server-side (i.e. off-device), and enables their access and ability to remove their Personal Data, if needed;
  • K-anonymity, which ensures protecting End Users’ Personal Data in the dataset via data masking, data generalization and/or replacement of the sensitive data elements with a hash;
  • Differential privacy, which implies adding extra noise to the aggregated datasets in order to ensure the impossibility to de-anonymize the individual’s Personal Data.

Key Benefits vs. Potential Challenges

One of the key benefits of Ad Selection API is its interoperability with Google’s Protected Audience API in terms of syntax, object structure (including Interest Groups, Topics, etc.), term definitions and the core functionality. This potentially leverages the common framework for the targeted online advertising in the cookieless environment, when it arrives, across browsers. 

However, handling computational tasks off-device contradicts Google’s Privacy Sandbox principles. This can prevent the full interoperability of both concepts and may put more pressure on the ad tech professionals to prevent unwanted access to their physical data centers. 

Another essential benefit is the preservation of the publisher-focused features by the Ad Selection API. Namely, these include dynamic creative selection, page capping, competitive exclusion, and multi-tag/-size support, which helps deliver responsive ads across all viewers’ devices and screens. 

Meanwhile, one of the potential drawbacks of the API is that the use of K-anonymity and differential privacy still can’t guarantee the 100% data anonymity, hence further constraints are likely to be introduced along the way, e.g. injecting even more noise to datasets, which will inevitably result in lower audience addressability.

Perspectives of Adoption

While Microsoft is planning to experiment with the cookie phase-out on a certain, small percentage of devices (with commercial customers and their managed devices are promised not to be impacted, though) throughout 2024, the company encourages its partners to test out and adopt its Ad Selection API in the second half of the year. 

This, obviously, means that the wide adoption of the Ad Selection API won’t happen until H2 2025, or even further on in time.

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