The Privacy Sandbox is Google's initiative to replace third-party cookies in Chrome with privacy-preserving web APIs that support advertising without cross-site user tracking. Announced in 2019, it aims to let advertisers target and measure campaigns while keeping behavioral data on-device. Key APIs include Topics API (assigns ad interest categories from local browsing history), Protected Audience API (enables remarketing without cross-site tracking), and Attribution Reporting API (measures conversions without exposing user-level data). Google's deprecation timeline has been delayed multiple times. As of 2026, Chrome is implementing cookie partitioning (CHIPS) alongside Privacy Sandbox APIs while phasing out unpartitioned third-party cookies.