Launched in 2007, tumblr became a safe haven for LGBT youth, social justice movements, and a counseling station for mental health issues. For a decade, this micro-blogging platform had more users than either Twitter or Snapchat, but it remained an obscure subculture for nonusers. Katrin Tiidenberg, Natalie Ann Hendry, and Crystal Abidin offer the first systematic guide to tumblr and its crucial role in shaping internet culture. Drawing on a decade of qualitative data, they trace the prominent social media practices of creativity, curation, and community-making, and reveal tumblr’s cultlike appeal and position in the social media ecosystem. The book demonstrates how diverse cultures can – in felt and imagined silos – coexist on a single platform and how destructive recent trends in platform governance are. The concept of “silosociality” is introduced to critically re-think social media, interrogate what kinds of sociality it affords, and what (unintended) consequences arise. This book is an essential resource for students and scholars of media and communication, as well as anyone interested in an influential but overlooked platform.