Linguistic diversity on the Internet is often said to be increasing, particularly by marketing research groups seeking to identify global trends in Internet business. This chapter addresses how well such statements reflect the reality of global linguistic diversity and online multilingualism, by applying a statistical index of diversity based on the notion of entropy. A comparison of the indexes for the marketing data and for global and regional demographics, as reported in the Ethnologue, shows that marketers’ statements both overstate Internet linguistic diversity and underestimate global linguistic diversity. Internet language diversity is similar to that seen in a typical South East Asian country, and is hundreds of times less than global linguistic diversity. Moreover, Internet resources are concentrated in the US and Europe, where linguistic diversity is very low. Indications are that Internet linguistic diversity is stabilizing at this modest level, rather than increasing, as has been previously suggested.