This work presents the development of the "Active Citizen Compass (ACC)", a digital assessment tool designed to evaluate active citizenship among secondary education students. The tool has been developed within the framework of the Erasmus+ project "Active Citizen Compass," which aims to promote active citizenship among students across six partner countries: Belgium, Czechia, Greece, Spain, the Netherlands, and Turkey. Before the tool’s development, a cross-national study was conducted to explore students’ knowledge, skills and attitudes related to active citizenship. The findings from this research informed the design of the ACC, which will be piloted in partner schools to assess students’ active citizenship competencies before and after participating in related learning activities. Upon completion, the tool will be freely accessible to all schools, supporting them in promoting and assessing active citizenship competencies in diverse educational contexts.