Across different national contexts public libraries have dealt, in diverse yet comparable ways, with the multiple challenges stemming from globalization, migration, marginalization and technological developments. This article argues, by way of dissecting three cases of library planning programmes which focused on centring libraries in their neighbourhoods, that we in recent decades witness the contours of a social library. Discussing experiences from initiatives in the UK, Canada and Denmark we, notwithstanding significant national differences, highlight common features – that libraries bring together already existing, but hitherto isolated institutional knowledge and competencies. We conclude by proposing a tentative typology of ‘the social library’.