Drawing on the example of the Great War, this article explores the process of constructing online collective memory, in which the key role of writing emerges. Writing serves both to interact in the collective space of the forum and to share individual research via online publications. A network of sites thus emerges around the forum: a mosaic of writings constituting virtual memorials in memory of a soldier or a regiment, based on archive documents that may be institutional or private, textual or photographic. The making of a collective memory of the Great War relies on a network of amateurs who, through the intensity of their interactions, produce and disseminate a shared way of remembering collectively. To study this community, an original survey system was set up which accounts for this plurality of writing formats. The research method is based on the first full-scale exploitation of web archives (a collection established by the Bibliothèque nationale de France) and combines quantitative processing with an ethnographic approach. It offers a resource to study other online phenomena that raise the question of the relationship to the past.