This chapter explores the development of the “Was That Ok?” tool, a youth-led digital resource designed to support young people experiencing or engaging in Harmful Sexual Behaviours (HSBs). Emerging from the Headstart project, the initiative responds to growing public concern around HSBs following the Everyone’s Invited movement and Ofsted’s review of sexual harassment in schools. Despite heightened awareness, young people reported a lack of trusted, practical information as well as confusion about what constitutes HSB. Many young people described adults’ tendency to overreact to issues as a barrier to seeking help. Using a harm reduction approach rooted in the ecological model, the project engaged 50 young people in co-designing the “Was That Ok?” tool. Focus groups identified the need for clear, honest information about the legal and emotional implications of HSBs, confidentiality, and available support. Participants sought guidance on dealing with problems themselves, as well as highlighting a need for honest information about what would happen if they disclosed HSBs. Consultation with professionals reflected a desire to simply encourage young people to report the issues they experienced, with little understanding of the barriers to reporting. The final tool integrates legal information, practical advice, and resources for victims, (potential) perpetrators, and bystanders, filling a critical gap in accessible, youth-friendly information.