In Europe, and globally, substantial numbers of young people are at risk of social exclusion, and there is therefore a pressing need to develop more knowledge and innovation to create more inclusive and youth-friendly societies. Citizen social science might contribute to these needs, but the actual outcomes of citizen social science and its innovative potential is uncertain. YOUCOUNT will therefore, through cocreative youth citizen social science (Y-CSS) including youths in the age of 15- 29 years as citizen scientists, produce new knowledge of positive drivers for social inclusion of youth at risk of exclusion, and cocreate innovations and policy-making. Moreover, to provide evidence of the actual outcomes of Y-CSS through hands on citizen science activities. The project includes four substudies: 1) Development of a framework for Y-CSS together with a transdisciplinary consortium and multilevel platform of key experts and stakeholders in a European and international setting. 2) Implementation of a multiple case study of Y-CSS projects in nine countries across Europe where over 900 young citizen scientists and nine local living labs will cocreate innovations together. 3) Mixed-methods evaluation of the outcomes and impact of the Y-CSS activities, and a multi-criteria assessment of the costs and benefits of Y-CSS, and 4) Creation of social and scientific impact through widespread scaling up and continuity. These activities will lead to robust knowledge and scientifically reasoned measures to promote Y-CSS and social change. The project will support dissemination and education in Y- CSS, and make synergies with other CS related projects and initiatives, in particularly with citizen social science.