Recently, the web industry has opened the possibility to phase out third-party cookies. Following the lead of the Safari and Firefox browsers, which block them by default, in 2019 Google announced the Privacy Sandbox initiative, a set of APIs designed to replace the functionality of third-party cookies in the Chrome browser. These APIs are designed to support advertising functionality, fight fraud and strengthen cross-site privacy boundaries, improving user privacy. This thesis investigates the Privacy Sandbox, with a particular focus on the Protected Audience API, which enables interest-based advertising and ad retargeting. The research objective is to evaluate the adoption and implementation in practice.