At the completion of each EMA, participants in the intervention group (n=50) will receive messages that address:1) unsafe sexual behaviors, 2) alcohol/drug use, 3) PrEP interest, and 4) HIV testing. In addition, participants will have access to a button in the app that will link them to resources when/if they are the victim of sexual assault. Finally, intervention arm youth will be asked to set a behavioral goal related to HIV prevention during this session. Those goals will include increasing condom use, PrEP use, non-occupational post-exposure prophylaxis (nPEP) use, reducing number of sexual partners, not having sex with using drugs or drinking alcohol, avoiding IV drug use, getting testing for HIV, and testing and treating sexually transmitted infections (STIs) as needed

Number recruited is number of eligible youth minus number who refuse to participate.

The System Usability Scale (SUS) consists of 10 items on a 5-point (0-4) Likert scale and is designed to assess acceptability of a product. Overall score ranges from 0 to 100, with higher scores indicating greater acceptability.

The Mobile App Rating Scale (MARS) consists of 23 items on a 5-point (1-5) scale is designed to score apps on the criteria of engagement, functionality, aesthetics, and information quality (sub-scales). Total score is determined by calculating the mean of each sub-scale and an overall mean score. High mean scores indicate a higher quality app.