Google Privacy Sandbox introduces on-device browser auction mechanics that replace cross-site tracking with privacy-preserving APIs.
Topics API vs. Protected Audience API
The Topics API categorizes user interests directly within Chromium based on weekly browsing history, exposing coarse, top-level interests to ad networks without persistent fingerprinting. Meanwhile, the Protected Audience API executes client-side remarketing auctions inside secure browser worklets, keeping sensitive user identifiers shielded from third-party observation.