In years 1-3 of the iTech, we will have optimized and pilot-tested using a similar study design and identical study outcomes two distinct mobile apps, LYNX and MyChoices, designed to increase HIV testing and PrEP uptake among YMSM. The apps were developed based on different theories of behavior change, and therefore contain different components, differing messaging strategies and different approaches for engaging youth. If either or both apps are shown to be both feasible and acceptable, the individual apps will be tested in this follow-on research study in Years 4 and 5 to evaluate for efficacy. Comparing the apps will allow us to identify any efficacy differences in increasing HIV testing or increasing PrEP uptake between the two apps. If justified, we will combine the components of each app that have the greatest impact on behaviors into a final, composite app for dissemination.