 The study aims to explore user experiences of and reasons for engaging and not engaging with a wide range of health and well-being apps among adults in the United Kingdom. The results suggest that factors such as available user guidance, statistical and health information, reduced cognitive load, well-designed reminders, self-monitoring features, safety net features, tailoring, peer support, embedded professional support, feedback, rewards, encouragement, goal-setting, action planning, self-confidence, and commitment are important for increasing effective engagement with health and well-being apps. This article was authored by Dorothy Sinay, Olga Persky, Andy Jones and others.