On December 20, 2017, and April 10, 2018, respectively, the Court of Justice of the European Union passed two landmark cases on the legal status of internet platform Uber. The Court established that Uber does not merely provide an app, but rather offers a full transport service. Without Uber there would be no market for non-professional drivers using their own vehicles. Moreover, the platform exercises a decisive influence over the conditions under which drivers provide their service. These rulings address the very core of several highly debated questions on the legal status of online intermediaries such as Uber, Airbnb and TaskRabbit. Emerging platforms claim to create new market opportunities and to provide innovative solutions to improve social welfare. Conversely, the platform economy blurs established lines between traditional legal categories, such as business and consumer, personal and professional, and worker and contractor. Traditional regulation, which often focuses on balancing the interests of two contracting parties, is now confronted with the three-sided contractual relationship between a platform, a supplier and a user. In this book, a panel of international legal experts unravel the legal status of online intermediaries – a thorny knot that legislators, judges and lawyers across the globe are facing.