This study investigates how effective a mobile app is in helping adolescents manage asthma. Asthma is a condition where the airways in the lungs become narrow and inflamed, making it hard to breathe. The app is a mobile version of an asthma action plan and aims to provide real-time, personalized feedback, asthma education, and data logging/tracking capabilities.

Participants in the study will be divided into three study arms. Each arm will follow different procedures to assess the app's effectiveness. The app will be tested for its ability to improve asthma management by providing personalized feedback and education to the users.

• Who can participate: Participants must be aged 12 to under 21 years, have persistent asthma, and an ACT score of 19. They need a preventive asthma medication prescribed in the last 6 months and access to a compatible smartphone and the internet.
• Study details: Participants will use a mobile app designed to assist in managing asthma. The app provides real-time feedback and educational content to help track and manage asthma symptoms. A placebo is not used in this study.