The sharing economy harbours a diversity of stories and practices that make this notion somewhat ambiguous. On the one hand, some powerful platform-companies, designed to capture, process and control increasing volumes of data in the hope of generating high profits, claim to belong to the sharing economy. On the other hand, we find sharing platforms that aim to escape purely commercial principles and place sharing and solidarity at the heart of their development models. A qualitative study carried out in France with a sample of nine platforms belonging to this second type brought to light two findings. Firstly, the alternatives studied are characterised by a dynamic of "re-embedding" on at least one of the three fictitious commodities identified by Polanyi (labour, money and land). Secondly, they aim to go beyond the classical opposition between the open strategy of the digital commons and the more closed approach based on collective ownership found in platform cooperativism. They manage to overcome this opposition through mutualistic practices and alliances, and multi-stakeholder governance built around the general interest. In doing so, sharing platforms are inventing the outlines of a possible renewal of public action and laying the foundations for an organised response to the challenges of the social and ecological transition