The NHS needs effective quality improvement interventions to be put into clinical practice, which requires effective behaviour change interventions. Intervention modelling experiments (IMEs) are a way of exploring and refining an intervention before moving to a full-scale trial. They do this by delivering key elements of the intervention in a simulation that approximates clinical practice by, for example, presenting GPs with a clinical scenario about making a treatment decision. Earlier IMEs have been paper-based, which limits what can be done in the simulation.