Digital platforms provide many workers with vital income and offer the promise of flexible work, and yet also contribute to experiences of precariousness and exploitation, particularly with regard to pressures to undertake unpaid work. This article explores why unpaid labour is necessary and what drives its extent and form among diverse types of digital platforms. We theorize two ideal types of ‘open’ and ‘closed’ socio-technical platform regimes of worker autonomy, building on sociological insights about socio-technical systems, management control over worker autonomy and labour market segmentation by skill. In principle, ‘open’ (‘closed’) platform regimes grant relatively high (low) worker autonomy in terms of access to the platform, paid work and control over work tasks. Analysing five case studies, illustrative of ‘open’ and ‘closed’ regimes, we investigate unpaid labour in low-skill locational (i.e. food delivery) platforms and medium/high-skill online (i.e. freelancing) platforms. In brief, digital freelancers exhibit a lower extent of unpaid labour within relatively ‘open’ regimes, owing to greater autonomy over access to, and control over, platform work in a sector requiring medium/high skills. Conversely, ‘closed’ regimes mitigate unpaid labour for food-delivery platforms by providing market shelter for workers, who are easily replaced in an overcrowded sector requiring few skills.