Involving girls in urban development will make the city better for everyone. Girls plan and design with diversity and different needs in mind. Participatory processes are key for planning a city that works for everyone. If we let citizens that are rarely heard be the experts, our cities and communities will become more inclusive, equal and sustainable. The purpose of this initiative is to make methods and tools available to urban actors and cities globally. We support cities to scale up and mainstream girls’ participation in planning as a part of their long-term strategies to build sustainable cities and societies. Together with experts and stakeholders in urban development, we have created a toolbox with a cost-efficient process to be incorporated within cities and communities. The toolbox follows a unique process containing 9 building blocks as a digital guideline on how to co-plan cities from a girl’s perspective.