We describe the degree of formality of language in French politicians’ blogs, with specific focus on comparing blog posts and blog comments. The degree of formality is investigated in a corpus of posts and comments in 80 blogs through a cluster of features derived both from traditional French sociolinguistics and from studies of informal computer-mediated communication. The features examined are 1) syntactic (omission rate of the negative particle ne and forms of Yes/No-questions), 2) lexical (frequency of colloquialisms and of acronyms and non-standard spelling), and 3) prosodic (frequency of repetitive punctuation and emoticons). The analysis shows that the language used in the French politicians blogs is overall relatively standard. However, the language politicians use in their blog posts is more standard than the language used by commenters – the latter ranges from strictly formal to highly colloquial.