This paper presents a sociolinguistic perspective on language in the Internet. Most linguistic research on computer mediated communication has focused on media or genre related language variation, establishing language styles as typical for e.g. chat or newsgroups. A critical discussion of this research suggests that more attention should be paid to user related language variation. The concept of ‚online community‘ is proposed as a suitable starting point for the study of language variation on the Internet, and sociological and linguistic criteria for the definition and description of online communities are discussed. The second part of the paper presents a classification of sociolinguistically relevant variation patterns. Finally, evidence for the effect of various social factors on language use in the Internet is reviewed.