Young people are often unaware what combinations of drugs they are taking, and drugs such as ecstasy or cocaine can contain deadly substances such as powerful synthetic opioids. Our codesigned project with a team of people who use drugs, service providers, toxicologists, analytical chemists and researchers will invite young people aged 16 to 24 attending music festivals and school leavers celebrations in the ACT, Vic and WA to complete anonymous surveys before and after these events, and through short daily surveys via mobile phone. Combining state-of-the-art social research and drug identification technology the research will also incorporate data from drug checking and health services to build a clearer picture of what substances people have actually used and how they affect their mental and physical health. It will engage with services and young people with lived experience to codesign effective responses to prevent and manage health harms.