We all want cities, where more than half of the world’s population currently live, to be just, successful, clean, fair, green, sustainable, safe, healthy and affordable. Will ‘smart cities’ help achieve these aspirations or undermine them in the time of COVID-19? Phil Allmendinger, a world expert on cities, development, and urban governance, takes a critical approach to the role of ‘smart’ in future cities and the relationship with city development. Considering how technology can support active citizenship, he challenges the commercial drivers of big tech and warns that these, not developments for ‘social good’, may dominate. Focusing on the dangers posed by social media, the platform economy and AI, he sets out what those making decisions on city development need to understand in order to save the planet through active politics and healthy cities.