This book examines users' digital content contribution and consumption behavior from a social perspective. Digital content is everywhere--from search results on search engines to posts on social media. Incentivizing users to contribute abundant content and motivating users to engage in and pay for digital content are vital for online platforms, especially those relying on digital content generated by users. This book develops a theoretical framework to incorporate social influence, including social presence, social interaction, social comparison, social loafing, and social relationships, in users' digital content contribution and consumption decisions. Further, using a large volume of data from online platforms, the author empirically studies the role of social interaction in digital content provision and monetization from the supply side. Also, regarding the digital content demand side, this book explores how to boost content consumption via social motives and social norms. The book enriches the understanding of social influence in digital content contribution and consumption and provides practical suggestions for digital platforms' mechanism design.