Since their release in 2005, Google Maps-based tools have become the de facto solutions for a variety of online cartographic projects. Their success has been accompanied by a range of critiques denouncing the individualistic market-based logic imposed by these mapping services. Alternative options to this dominant model have been released since then; uMap is one of them. uMap is a free, open-source online mapping platform that builds on OpenStreetMap to enable anyone to easily publish web maps individually or collaboratively. In this paper, we propose to reflect on the potential and limits of uMap based on our own experiences of deploying it in six different mapping projects. Through these experiences, uMap appears particularly well-suited for collaborative mapping projects, due to its ease in connecting to remote data and its high level of interoperability with a range of other applications. On the other hand, uMap seems less relevant for crowdmapping projects, due to its lack of built-in options to manage and control public contributions. Finally, the open-source philosophy of uMap, combined with its simplicity of use and its strong collaborative capacity, make it a great option for activist mapping projects as well as for pedagogical purposes to teach a range of topics including online collaborative cartography.