This book examines the transformation of online targeting in a world of increasing privacy regulation, declining third-party identifiers, and growing reliance on first-party data. It provides practical guidance for marketers, technology teams, and decision makers who need to build sustainable digital advertising and data strategies. The authors explain how organizations can develop privacy-compliant targeting capabilities based on first-party data, identity resolution, and modern marketing technology architectures. They evaluate emerging approaches from both advertiser and publisher perspectives and show how companies can maintain effective targeting, measurement, and personalization in a cookieless environment. Without consistent and privacy-compliant customer recognition across touchpoints and devices, organizations risk fragmented customer views, inefficient advertising spend, and unreliable attribution. This book outlines concrete strategies to overcome these challenges and build a future-ready foundation for data-driven marketing.