This book offers a comprehensive scholarly overview of Reddit, one of the most popular and least studied social platforms of the early 21st century. The book inspires new ways of thinking about Reddit, considering it from multiple perspectives: through a historical lens, as a site where identity is forged, as a democracy, as a community, and as a news aggregator and distributor. By bringing theories from computer-mediated communication, communication studies, and sociology to bear on original, large-scale observational analyses of Reddit’s communities, this book provides a uniquely comprehensive overview of the platform’s first 15 years. Understanding Reddit will help us make sense of how rapidly growing communities function in an era of mass online anonymity. Serving both as a primer on how social behavior on Reddit plays out, and as a way of locating it within multiple theoretical traditions, the book will offer important insights to scholars and students in the disciplines of communication, media studies, information science, internet and emerging media studies, and sociology.