P3 (Prepared, Protected, Empowered) is a three arm, randomized-controlled trial (RCT) that will test the efficacy of the P3, a novel, theory-based mobile app that utilizes game mechanics and social networking features to improve PrEP adherence, retention in PrEP clinical care and PrEP persistence among young men who have sex with men (YMSM) and trans women who have sex with men (YTW), ages 16-24.