One of the main characteristics of Web 2.0 relational platforms is the close articulation between the way in which users present different features of their identity, and the visibility that the platform grants them. The aim of this article is to propose a framework of interpretation for a wide variety of relational platforms (meeting sites, intimist blogs, social networks, sharing of content, micro-blogging, virtual world). The author characterizes the different identity formats that participants produce, and the modes of visibility afforded them by the platforms. He then examines the plurality of forms of identity, the diversity of forms and sizes of social networks on Internet, and the originality of forms of navigation on these platforms.