Low-carbon lifestyles – from eating less meat, swapping the car for a bike, and switching to energy efficient devices – can help reduce greenhouse gas emissions. The EU-funded CAMPAIGNers project aims to revolutionise the way lifestyle transformation research is conducted and how it informs policies. Specifically, it will move from hypothetical citizen behaviour to the implementation of a goal-setting network where over 100 000 citizens receive and create challenges to try out tailored adaptations to their daily routines via an engaging app. The project will identify the barriers and enablers across 5 continents and 16 major cities. The findings will be used to design feasible pathways to reducing greenhouse gas emissions.