Digital health behavior interventions may offer scalable ways to prevent type 2 diabetes among adults at increased risk for the disease, with minimal burden on health care systems. However, ensuring implementation in routine care as well as continued engagement by end users are challenges impacting the expected effectiveness at individual level as well as wider public health outcomes. In this presentation, Prof Pilvikki Absetz describes the design of a habit-based health behavior app, the BitHabit, which was implemented as part of preventive care pathways in collaboration between the Stop Diabetes project and the primary health care of three provinces in Finland. She also presented findings on user engagement and how it relates to effectiveness, based on an unblended parallel RCT and longitudinal data from 1926 participants receiving the digital intervention. Finally, she discussed some of the challenges and implications of engagement and implementation for public health impact.