Book excerpt: With the development of advanced media technologies, cyberspace is gradually transforming from temporal immersion into a state of new normal. An increasing proportion of our daily lives has become a mix of physical and virtual worlds. As a complex social psychological phenomenon, online social identity has attracted widespread attention from academia to industry. Identity-related issues have been noted as an important subject of Internet interdisciplinary research, including social psychology, sociology, personality psychology, and health psychology. Communication in cyberspace always carries some degrees of anonymity, for users present virtual identities constructed by themselves in cyberspace, hiding their real identities and constructing their online identities as a form of social identity enactment. On the other hand, online media provides tools and environments for virtual identity building. Although the anonymity of the internet facilitates the subjects' construction of their virtual identity, their online virtual identity is not completely anonymous and can be identified and authenticated online, thereby meaning we can research how online identity relates to real world identity. Identification is a social process that matches internal self-identity with external identity types, and it is also a process and a reflection of internal perceptions, and mere identification with a group has been shown to dramatically affect behavior (as per social identity theory).