With increasingly accessible camera technology, crowdsourced public media projects abound like never before. Such projects often seek to secure a snapshot of a single day in order to establish communities and create visual time capsules for the future. Mass Photography: Collective Histories of Everyday Life assesses the potential of these popular moment-in-time projects by examining their current day prevalence and their historical predecessors. Through archival research and interviews with organisers and participants, it examines, for the first time, the vast photographic collections resulting from such projects, analysing their structures and systems, their aims and objectives, and their claims and promises. The central case study is the 55,000 photographs submitted to One Day for Life in 1987, which aimed, in its own time, to be 'the biggest photographic event the world had ever seen'.