What unites Google and Facebook, Apple and Microsoft, Siemens and GE, Uber and Airbnb? Across a wide range of sectors, these firms are transforming themselves into platforms: businesses that provide the hardware and software foundation for others to operate on. This transformation signals a major shift in how capitalist firms operate and how they interact with the rest of the economy: the emergence of 'platform capitalism'. This book critically examines these new business forms, tracing their genesis from the long downturn of the 1970s to the boom and bust of the 1990s and the aftershocks of the 2008 crisis. It shows how the fundamental foundations of the