This article draws on the concept of communities of practice (COP) in order to illuminate the phenomenon of ‘indie unions’ and their contribution to the UK labour movement. These unions are typically regarded as distinct from, and perhaps in opposition to, existing labour movement institutions, and thus exempt from consideration in debates about union renewal. The argument offered here aims to show that by conceptualising the UK labour movement as COP, and the indie unions as community members, they can be considered key actors in union renewal. Through case studies of different union campaigns in the outsourced cleaning sector, this article demonstrates how the indie unions’ strategies are being learned and practised by the established unions, thus situating them as an intrinsic part of a stratified yet solidaristic labour movement with the potential for renewal.