BackgroundThe prevalence of cannabis use disorder and its negative consequences among young adults has highlighted the need for prevention and early intervention programs. However, low treatment prevalence persists due to factors such as lack of perceived need, concerns about stigma, and limited access to treatment. To address these barriers, web-based cannabis interventions have been developed, but their efficacy remain limited. This study aims to evaluate the cross-site efficacy of the Cannabis eCHECKUP TO GO program, a web-based Personalized Normative Feedback and Protective Behavioral Strategies intervention for reducing cannabis use frequency and consequences in college students with willingness to change. MethodsParticipants were 781 students from three universities (two in Canada, one in the US) who reported using cannabis in the past month and expressed interest in reducing or engaging in safer cannabis use. The study randomly assigned them to either an experimental group that received personalized normative feedback or a control group that received information on healthy stress management. The study collected follow-up data 4 weeks after the initial intervention and measured participants' frequency of cannabis use, number of cannabis consequences, descriptive and injunctive norms at both time points. ResultsThe results showed no significant reductions in cannabis use or negative consequences of use. However, students who received personalized normative feedback experienced a significant reduction in descriptive norms related to cannabis use, to be more in line with actual use. ConclusionThis study suggests that more targeted interventions may be necessary for university students who are already using and seeking help to reduce their use.