© 2017 The Authors.Risk-adjusted survival statistics after children's heart surgery are published annually in the United Kingdom. Interpreting these statistics is difficult, and better resources about how to interpret survival data are needed. Here we describe how a multidisciplinary team of mathematicians, psychologists, and a charity worked with parents of heart surgery children and other users to codevelop online resources to present survival outcomes. Early and ongoing involvement of users was crucial and considerably changed the content, scope, and look of the website, and the formal psychology experiments provided deeper insight. The website http://childrensheartsurgery.info/ was launched in June 2016 to very positive reviews.