Google announced on Tuesday that it's officially rolling out Privacy Sandbox on Android in beta to eligible mobile devices running Android 13.

"The Privacy Sandbox Beta provides new APIs that are designed with privacy at the core, and don't use identifiers that can track your activity across apps and websites," the search and advertising giant said. "Apps that choose to participate in the Beta can use these APIs to show you relevant ads and measure their effectiveness."

Devices that have been selected for the Beta test will have a Privacy Sandbox section within Settings so as to allow users to control their participation as well as view and manage their top interests as determined by the Topics API to serve relevant ads.

The initial Topics taxonomy is set to include somewhere between a few hundred and a few thousand topics, according to Google, and will be human-curated to exclude sensitive topics.

The Beta test is expected to start off with a "small percentage" of Android 13 devices and will gradually expand over time.

The Privacy Sandbox on Android is Google's answer to Apple's App Tracking Transparency (ATT), which requires app developers to seek users' explicit consent before tracking their online behavior across apps and websites through unique identifiers. It was introduced by Apple in iOS 14.5.

The experiment is part of a broader initiative for the web that also aims to begin phasing out third-party cookies in the Chrome web browser by 2024.

The technology that underpins its ability to glean users' evolving interests is a machine learning technique called federated learning that decouples the "ability to do machine learning from the need to store the data in the cloud."

This effectively allows decentralized edge devices such as smartphones to learn a shared prediction model while keeping all the training data on device, thereby making it possible for websites to access information about consumers without compromising user privacy.

Currently, Android devices are assigned a unique user-resettable identifier that can be used by app developers for tracking online behavior. Privacy Sandbox replaces the identifier with a set of privacy-preserving tools that are engineered to limit information sharing and at the same time support personalized ads.

While Google's proposals hope to strike a balance between interest-based advertising and privacy, the company also criticized that "blunt approaches" such as those from Apple don't provide viable alternatives.

That having said, Apple's ATT has faced criticism of its own. In September 2021, Lockdown Privacy called Apple's policy "functionally useless in stopping third-party tracking" and that it "made no difference in the total number of active third-party trackers."

What's more, a report from the Financial Times in December 2021 found that apps are continuing to track users on iOS, albeit in an anonymized and aggregated fashion similar to Google's Privacy Sandbox.