Digitally mediated participatory mapping (DGPM) has expanded significantly in recent years, along with the growth of open‐source mapping. Grassroots sustainability initiatives have exploited this opportunity, and today there are hundreds if not thousands of maps of these projects in locations around the world. However, to date little scholarly attention has been paid to participatory internet‐based mapping of grassroots sustainability projects. In this article, we begin to fill this gap by examining the potentialities and limitations of DGPM for grassroots sustainability projects from a critical geographic information systems perspective. Specifically, we investigate issues of participation, knowledge, and inclusion; and access, visibility, and sustainability. We also explore the benefits and complexities of these maps for local users and in the context of broader sustainability transitions. In so doing, we draw from our experience of participating in the process of creating and maintaining the Utah Resilience Map. We conclude with suggestions for future research in the field of participatory mapping of sustainability transitions.