Illicit drug use among higher education populations is a recognized public health issue. Brief personalized digital behavior change interventions with targeted harm-reduction can facilitate immediate support for this population. To make the intervention tailored to students’ needs, we built a clinical algorithm, informed by relevant behavior change theories and with system design features. Given the lack of previously relevant harm-reduction at student population level, functioning with the use of an algorithm, the aim of this work is twofold. We firstly explain how we developed the clinical algorithm using an empirical data synthesis approach. Secondly, we illustrate how the algorithm is implemented within the first prototype of an intervention named MyUSE, by providing an example on how the clinical algorithm is used to allocate users into different personalized intervention components. The prototype is currently in its final development phase and subsequent work will focus on examining its usability, feasibility, and effectiveness.