The use of more than one language in SMS communication is widespread, yet has remained relatively underexplored in the existing research. In this paper we ask: What methodological and conceptual tools are needed for empirically investigating code-switching in large databases of SMS communication? We show that the investigation of SMS communication calls for an adaptation of the conceptual and the methodological apparatus of classical code-switching studies, which have been typically concerned with the analysis of spoken, mostly interactional, data. We argue for a broad understanding of code-switching that comprises switching between natural languages and language varieties along with style shifts as well as switching between language and other semiotic systems (ideographic switching). We also document, as a key feature of SMS communication, hybrid forms of language use that blur the boundaries between what we commonly call languages (e.g. homographs, mixed spellings or allogenisms), and we suggest that these possibly indicate that SMS communication has become one site where the tension between localized and globalized social practices is played out. The study presented here is part of an inter-university research project, entitled “SMS communication in Switzerland: Facets of linguistic variation in a multilingual country”, based on a corpus of 26,000 authentic messages collected between 2009 and 2011.