Little is known about users' intervention engagement and use patterns within eHealth interventions. We describe these patterns among young men who have sex with men (YMSM) who participated in a brief eHealth intervention designed to increase HIV testing. We merged pilot trial participants' survey data (N = 86) with their paradata (e.g., system data recorded during interaction with the intervention). We created engagement (time spent on components) and use (interaction with features) metrics, and explored whether they differed by participant characteristics. Racial/ethnic minorities clicked on fewer features (mean = 8.30) than non-Hispanic White men (mean = 12.00). Use was associated with older age (r = .19), greater educational attainment (r = .25), and a greater number of methods to connect online (r = .38). Paradata can help researchers understand how users interact with eHealth interventions, and inform which components to retain or redesign. Efforts to systematically collect, analyze, and report paradata in eHealth HIV prevention and care interventions are warranted.