to become or remain livable for their inhabitants and offer social and economic opportunities. Considering global trends such as climate change and resource scarcity, a major challenge of future cities will be to reduce urban footprints. Thus, reconnecting food production and cities offers promising potential. The diffusion of urban farming reflects a rising awareness of how food and farming can shape our cities. A growing number of urban farming projects exist in and on urban buildings, including open rooftop farms, rooftop greenhouses and indoor farming. These projects are characterized by the non-use of land or acreage for farming activities. The term ‘Zero-Acreage Farming’ (ZFarming) is used to represent these farms. ZFarming generates innovative practices that may contribute to a sustainable urban agriculture. Besides growing food, it produces a range of non-food and non-market goods. It involves new opportunities for resource efficiency, new farming technologies, specific implementation processes and networks, new patterns of food supply and new urban spaces.