The book The Digital Markets Act (DMA) is an ex ante regulation of large digital platforms that act as gatekeepers. It not only contains many new rules for gatekeepers but also has a direct impact on all users of these platforms. The Practitioner's Guide is an easyto-use introduction to this highly complex subject. It makes the new law accessible and offers answers to the most important questions, including: * How are gatekeepers identified? * What are the specific duties of conduct imposed on gatekeepers? * What powers do the EU Commission and national authorities have over gatekeepers? * To what extent do business users (especially in