Social media are an important tool for building reputations. Adolescents use them to assert themselves among their peers, while avoiding adult supervision. There is still very little research on Snapchat, yet it has become the favourite network of young people and the fear of education professionals. This network is characterized by the ephemerality of the content exchanged and by the invisibility of the community. Drawing on a five-month (n)ethnographic survey in four schools in Ile-de-France, I describe the uses that middle-school students make of this network and explain why young girls from working-class neighbourhoods expose themselves to more reputational risks in using it.