Many science facilities are now providing open access to their data, making them findable, accessible, interoperable and reusable. By far the widest constituency of data users and contributors is the science-inclined public, for whom citizen science is the natural mode of engagement. However, 'citizen science' means different things to different communities. For some it means co-creation of research projects, while for others it means volunteer contributions to data collection or data mining being run by experts. Both approaches require dialogue and debate between the public volunteers and professionals.

This workshop will explore the best practices from these radically different approaches in different disciplines, the common challenges encountered, and lessons learned. Our focus will be on practicalities and live demonstrations. We will begin with short plenary presentations from experienced stakeholders in citizen science across many disciplines, from biological sciences and ecology to archaeology and the humanities to astronomy and physics. We will invite short technical presentations on the citizen science functionalities being developed (or still aspirational) in the European Open Science Cloud by research infrastructure clusters and e-infrastructures. This will be followed by engaging live demonstrations, then we will convene a lively panel discussion on lessons learned and best practices. In parallel, and in real time, recommendations will be collated into a live document of conclusions and recommendations, which will be submitted shortly after the workshop to a suitable journal and published under green or gold open access.