BackgroundTo date, non-occupational postexposure prophylaxis (PEP) has been widely accepted as a safe and effective intervention for HIV in many countries, yet it remains an underutilized prevention strategy in China. Evidence indicated a high demand for PEP among Chinese men who have sex with men, but the uptake and access to PEP service remain limited. In an era of rapid development of web-based technology, online medical platforms in China hold great promise in facilitating PEP provision and delivery by addressing problems such as accessibility, convenience, privacy protection, and antidiscrimination by integrating online and offline resources. However, there is a paucity of data concerning the uptake and outcomes of online PEP in China.ObjectiveThe aim of this study is to explore online PEP service provision and understand PEP uptake and outcome through a web-based cross-sectional study.MethodsFrom January 2020 to June 2021, we conducted a retrospective web-based survey among those seeking online PEP services via the internet medical platform “HeHealth” using a structured questionnaire. Participants were surveyed on sociodemographic characteristics, sexual and drug-related behaviors, history of preexposure prophylaxis (PrEP) usage, and PEP uptake. Statistical analysis included descriptive analysis, chi-square test, and multivariable logistic regression.Pvalues <.05 were deemed statistically significant.ResultsNo HIV seroconversions were observed among 539 PEP users. Our sample demonstrated that most participants seeking online PEP services were gay (397/539, 73.7%), single (470/539, 87.2%), having an education of more than 12 years (493/539, 91.5%), and with an average monthly income of 7000 RMB (1 RMB=US $0.14) or more (274/539, 50.8%). Sexual exposures accounted for 86.8% (468/539) of the cases, with anal sex being the most common indication (389/539, 72.2%) for seeking PEP use. Among 539 participants, 60.7% (327/539) sought online PEP for relatively low-risk exposures, whereas 39.3% (212/539) were considered high-risk exposures. Nearly all (537/539, 99.6%) initiated PEP within 72 hours and 68.6% (370/539) within 24 hours of exposure. All users (539/539) were prescribed a 3-drug regimen, with most comprising 3TC/TDF+DTG (lamivudine, tenofovir disoproxil fumarate, and dolutegravir; 293/539, 54.4%), followed by FTC/TDF+DTG (emtricitabine, tenofovir disoproxil fumarate, and dolutegravir; 158/539, 29.3%). The adjusted model showed that greater odds of PrEP usage were associated with an age of 35 years or older versus the age group of 25-34 years (adjusted odds ratio [AOR] 2.04, 95% CI 1.24-3.37), having an education of 17 years or more versus an education of 12 years or less (AOR 3.14, 95% CI 1.29-7.62), average monthly income of 20,000 RMB or more versus less than 3000 RMB (AOR 2.60, 95% CI 1.09-6.23), and having high-risk sexual behavior during PEP treatment (AOR 2.20, 95% CI 1.05, 3.69).ConclusionsThe 0% infection rate in this study demonstrated that online PEP could be a valuable risk-reduction option to improve HIV prevention service within China. However, further research is needed to better facilitate PrEP transition among online PEP users.