Research in computer-supported cooperative work has historically focused on behaviors of individuals at scale, using frames of interpersonal interaction such as Goffman's theories of self-presentation. These frames prioritize research detailing the characteristics, personal identities, and behaviors of large numbers of interacting individuals, while the social identity concepts that lead to intra-and inter-group dynamics have received far less attention. We argue that the emergent properties of

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... self-categorization and social identity, which are particularly fluid and complex in online spaces, provide a complementary perspective with which to re-examine traditional topics in social computing. We discuss the applicability of the Social Identity Perspective to both established and new research domains in CSCW, proposing alternative perspectives on selfpresentation, social support, collaboration, misbehavior, and leadership. We propose a set of methodological considerations derived from this body of theories and accompanying empirical work. We close by considering how broad concepts and lessons from social identity provide a valuable lens for inspiring future work in CSCW. Research in Computer-Supported Cooperative Work (CSCW) has explored the evolution of collaboration and cooperation in online systems since the early years of social computing. Findings have guided the development of systems and the formulation of theoretical models explaining the ways humans engage with them. However, the major methodological and theoretical approaches within CSCW have focused on individuals, whether in groups or at scale, as the unit of analysis, rather than focusing specifically on groups and their participation within online spaces. From foundational theory in social psychology, we know that the process of transitioning into groups can mean that