While life-as-usual remains disrupted by the COVID-19 pandemic, cities rely increasingly on community-based and often digitally-enabled sharing of knowledge, skills and resources. These emergent forms of ‘communal sharing’ cannot be explained through instrumentally-beneficial economic discourses or structurally-disruptive political narratives alone. Rather, they call for revaluing the interdependent social relations that digital platforms enable and maintain. Drawing from a relational ontology of transformative social innovation, this paper begins to reframe communal sharing as inherently interdependent social relations between citizens and across civic, market and government domains. These interdependencies mean that sharing through digital platforms is not only responding to, or resisting, dominantly neoliberalist urban logics but is both formed by and reforming new understandings of urban agency. To explore these new understandings of being, doing and thinking of the city as shared, the paper adopts a generative epistemology of postcapitalist politics. Reading communal sharing as not merely interdependent but as fundamentally prefigurative of urban structures, norms and behaviours, the paper develops a post-structuralist approach to sharing cities. This approach illustrates practices as co-determined, communities as resourceful, and initiatives as highly adaptive socio-spatial performances taking place within and beyond digital platforms. Recognising and nurturing the enabling role of digital in sharing cities, the paper adopts the hopeful stance of reconceptualising communal sharing to open space for social and sectoral divides to be bridged and reimagined beyond the pandemic accelerations of platform capitalism.