Introduction
sexual behaviors, MSM
STIS, HIV INFECTION, HEPATITIS C INFECTION
“Chemsex” is defined as the use of psychoactive substances before or during planned sex to facilitate, initiate, prolong, sustain, or intensify the sexual encounter [Empirical studies have reported that the practice of risky sexual behaviors is prevalent among MSM who engage in chemsex. A systematic review reported that the prevalence of condomless sex ranged from 17% to 100% among MSM who engaged in chemsex [MSM who engage in chemsex experience higher rates of HIV infection, other STIs, and hepatitis C infection than those who do not [Globally, “undetectable equals untransmittable (U=U)” and pre-exposure prophylaxis (PrEP) have become important elements in HIV prevention programs [In addition, even though PrEP is a very effective HIV prevention method [eHealth, health services and information delivered electronically through the internet (eg, through a website) [Although several systematic reviews have provided robust evidence about the effectiveness of eHealth interventions in improving sexual health among MSM [We hypothesized that the web-based intervention could increase participants’ self-efficacy in refusing risky sexual behaviors and chemsex, reduce both the intention to engage in chemsex and actual chemsex behaviors, enhance consistent condom use, and increase the uptake of HIV and STI testing.