UPSCALE is an international collaboration of universities, research institutes, public libraries, and non-governmental organisations (NGOs) that explore the preconditions for and possible upscaling of collaborative consumption using public libraries. UPSCALE runs until autumn 2024, and results will be published continuously in journals dealing with library and information studies, climate research, and sustainability. In this research note, we introduce ongoing research from the UPSCALE research group by presenting several case studies that show how public libraries act as change agents in different ways regarding sustainable development. This might be by facilitating, promoting the lending, and sharing alternative collections in the library or by building collaborations, partnerships, and networks with local community actors, NGOs, and other local and national partners.