Since the mid-twentieth century, treatments of code switching and associated practices have converged toward understanding linguistic hybridity and diverse sociality amid accelerating globalization of peoples, social groups, and commodified languages. This chapter reviews four traditions of code switching research that suggest divergent theoretical perspectives on language and identity. The first, established in the 1960s within the ethnography of communication, situates code switching as a product of local speech community identities. Research on language and political economy in the 1980s initiated a second tradition, which analyzes language alternation with reference to the contrastive nation-state identities constituted through processes of nationalism. A third tradition, influenced by the discursive turn in the 1990s, views code switching as a resource in urban minority communities for the performance of multicultural and interethnic identities. A fourth tradition, developed since the millennium, focuses on hybrid identities as the social corollary to the language mixing brought about through accelerated globalization.