Book excerpt: This book explores how the complex scenario of platforms, practices and content in the contemporary digital landscape is shaping participatory cultures of health and illness. The everyday use of digital and social media platforms has major implications for the production, seeking and sharing of health information, and raises important questions about health peer support, power relations, trust, privacy and knowledge. To address these questions, this book navigates contemporary forms of participation that develop through mundane digital practices, like tweeting about the latest pandemic news or keeping track of our daily runs with Fitbit or Strava. In doing so, it explores both radical activist practices and more ordinary forms of participation that can gradually lead to social and/or cultural changes in how we understand and experience health and illness. While drawing upon digital media studies and the sociology of health and illness, this book offers theoretical and methodological insights from a decade of empirical research of health-related digital practices that span from digital health advocacy to illness-focused social media uses. Accessible and engaging, this book is ideal for scholars and students interested in digital media, digital activism, health advocacy and digital health.