This book presents an in-depth study of the abuse of dominance in the platform economy. It starts by studying platform business strategy and then systematically analyzes how different forms of leveraging abuse (tying, refusal to supply, margin squeeze, discrimination) should be reinterpreted in the platform economy. The book also recognizes the procompetitive role of platforms and suggests safeguarding it by duly considering justifications. Finally, the book surveys ex ante measures targeted at platforms such as non-discrimination rules, portability and interoperability measures, forced access, and break-up.