Microsoft Edge has introduced its new Ad Selection API now that third-party cookies are being depreciated. This innovative feature is set to replace traditional third-party cookies, addressing the privacy concerns of users and regulators by using privacy-preserving advertising. The Ad Selection API is a browser platform feature that allows advertisers and publishers to display relevant ads to users without relying on third-party cookies or other cross-site tracking identifiers.
The Ad Selection API is part of Microsoft’s commitment to creating a more private web experience. It aligns with the industry’s shift towards greater data protection and user control over personal information. The API is built with robust privacy protections, including K-anonymity constraints, the use of differential privacy, and the safeguarding of user data throughout the ad auction process. These measures ensure that users can see relevant ads while maintaining full control of their data.
A key component of the Ad Selection API is the use of Trusted Execution Environments (TEEs), which allow for more computationally heavy tasks to be processed off-device. This means that no one can directly observe the data being processed, further enhancing user privacy.
The full proposal for the Ad Selection API is available on GitHub, and Microsoft encourages interested parties to engage with them directly through this project. The company is open to feedback and is collaborating with the web standards community and the web advertising industry to make further improvements.
Microsoft Edge will begin experimenting with the deprecation of third-party cookies in the coming months, targeting less than 1% of non-managed device users. This gradual approach will continue throughout 2024, allowing Microsoft to measure and evaluate the various impacts on customers and partners. The goal is to encourage the ecosystem to proactively prepare for the eventual removal of third-party cookies.
Commercial customers using Microsoft Edge on managed devices will not be impacted by these experiments. However, Microsoft strongly encourages commercial customers to begin testing their public and internal sites to ensure they and their partner ISVs have time to update their sites.
How to enable Ad Selection API in Microsoft Edge
For those interested in the Ad Selection API, more details will be shared as implementation progresses. Microsoft invites testing and adoption of the Ad Selection API by the industry in the second half of 2024, although this timeline is subject to change based on feedback and the impact on customers and partners.

To test third-party cookie deprecation in Microsoft Edge today, users can follow these directions:
- Navigate to
edge://flags/#test-third-party-cookie-phaseoutin a new tab. - Enable the “Test Third Party Cookie Phaseout” flag.
- Restart Microsoft Edge.
In the future, Microsoft Edge will generally block third-party cookies by default. However, the planned changes to third-party cookie deprecation will function differently than the current method of disabling third-party cookies via Edge settings. After the change, the browser will still allow explicitly partitioned cookies and automatically partition other storage, which is not shared across websites.
Web developers are recommended to test their site with this change to third-party cookies functionality. Proactive testing will enable developers to identify user experience impacts within their site and update on a timeline that they control.
This initiative by Microsoft reflects the growing importance of data protection and user privacy. The introduction of the Ad Selection API is expected to set a new standard for privacy in the digital advertising space, challenging other tech giants to follow suit, but only time will tell.
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