 This study aims to investigate the factors that encourage users to download smartphone fitness apps with the intention of being physically active. The study uses a confirmatory factor analysis and path modeling to test the hypotheses and explore the influence of moderators on structural relationships. The results show that habit, performance expectancy, facilitating conditions, price value, and effort expectancy are positively related to behavioral intention to use fitness apps, while social influence and hedonic motivation are non-significant predictors. Education-related app features moderate the association between performance expectancy and habit and app usage intentions, motivation-related features moderate the association of performance expectancy, facilitating conditions, and habit with usage intentions, and gamification-related features moderate the association between hedonic motivation and usage intentions. Age moderates the association between effort expectancy and usage intentions, and gender moderates the association between performance expectancy and habit and usage intentions. User experience was a non-significant moderator. The study identifies the drivers of the use of fitness apps and suggests that smartphone app features should be designed to increase the likelihood of app usage and physical activity by supporting users in achieving their goals and facilitating habit formation. Target group specific preferences for education dash, motivation dash, and gamification related app features, as well as age and gender differences should be considered. This article was authored by Yan Xiong Yong and Yurg Kieng Storfer. We are article.tv, links in the description below.