Data is not just the stuff of social scientific method; it is the stuff of everyday life. The presence of digital data in an ever-widening range of human relationships profoundly unsettles notions of expertise for both ethnographers and data scientists alike. This collection situates digital data in broader knowledge-production practices. It asks about the kinds of social worlds that data scientists are creating as the profession coalesces, and looks at the contemporary possibilities available to both ethnographers and their participants for knowing, formatting and intervening in the world. It shows what digital data is doing to the research methods that sustain claims to expertise, with a particular focus on implications for ethnography. The contributors offer empirically-grounded accounts of the cultures, infrastructures and epistemologies of data production, analysis and use. They examine the professionalization of data science in a variety of national and transnational contexts. They look closely at specific data practices like archiving of environmental data, or claims-making about how software is produced. They also provide a glimpse into the new methodological and pedagogical possibilities for teaching and doing ethnography in a data-saturated world. This book will be of interest to Anthropologists and ethnographers working at the intersection of social science and data science and of particular interest to applied ethnographers and students leaving graduate training who are figuring out how to use their skills in a data-centric world.