Perfectionism is elevated across, and increases risk for a range of Axis I disorders, as well as having a direct negative effect on day to day function. A growing body of evidence shows that cognitive behavioural therapy (CBT) reduces perfectionism and Axis I disorders, with medium to large effect sizes. Given the increased desire for online interventions to facilitate access to evidence-based therapy, web-based CBT self-help interventions for perfectionism have been designed. Existing interventions have not included personalised guidance which has been shown to improve outcome rates.