Social media has gone from being a buzzworld to being a part of people's everyday lives, as well as, a part of the daily work of different organizations. This study explores the interface between public libraries, users, social media, and the inherent information activities. The theoretical frameworks builds on research concerning information behavior, information practice, and information activities. The empirical investigations included questionnaires among library professionals and users, and a content analysis of public library Facebook pages. One of the main contributions is the mapping of seven information activities found among library professionals and users. These information activities help to draw a realistic picture of the social media and public library context. The study also contrubutes to an increased understanding of the relationship between library professionals and users, and their different perceptions of the interface between social media and public libraries.