Planning a web-based intervention to reduce the level of depression, we wanted to test its' effectiveness in a randomized controlled trial using a care as usual approach. Since the participants in the experimental group will be able to conduct this app in their own speed, possibly resulting in a number of people finishing the app before its' official post assessment after 12 weeks, we are a bit concerned to produce an extremely high ( > 50.00%) dropout rate, which I read is not too uncommon in web-based intervention research. So my question is:

What are your experiences regarding the dropout rate in web-based interventions using RCT? Did you find a succesful strategy to keep the dropout rate in both groups as low as possible?

Thank you so much in advance, I am looking forward to reading about your experiences.