Co-designed social media advertising for Headstrong: an app to help young people build resilience and a healthy outlook on life

: Headstrong is a free, evidence-based digital tool designed to support mental well-being among Indigenous youth (Rangatahi Māori) and other young people in Aotearoa New Zealand. Delivered through brief, chat-like sessions, the app offers a bicultural and bilingual experience that aligns with youth preferences and cultural contexts. : This study applied a co-design methodology to ensure that youth realities and perspectives informed mental health prevention strategies. Through a series of participatory workshops, young people collaborated to develop a social media advertising campaign aimed at increasing engagement with Headstrong. : Youth participants engaged in structured co-design workshops to explore barriers and facilitators to app engagement. Their input guided the creation of campaign content and format. : The thematic analysis of data from the workshops revealed that youth valued advertisements that reflected cultural diversity, affirmed individuality, conveyed a clear and direct message, were concise, and authentically represented the app interface. Participants proposed short-form videos to demonstrate real-world use of Headstrong, resulting in the “Highlighting Headstrong” campaign. : The co-design process enabled the development of a culturally resonant and youth-driven campaign that enhanced engagement with the Headstrong app. These findings underscore the importance of participatory design in the relevance and effectiveness of digital mental health prevention strategies for young people.