RecruitingDiagnostic testFeasibility of Internet-based HIV Prevention ResearchThe study will use social media to recruit a diverse sample of people who self-report injecting drugs, assessing the feasibility of online assessments and participants' ability to perform at-home self-administered HIV testing. Participants will complete online questionnaires at baseline and will be mailed HIV testing kits that they will self-administer and mail to a central laboratory. Investigators will track completion of questionnaires and whether at-home self-administered HIV tests were completed and sent to the laboratory.