Abstract
BACKGROUND: Unsafe sexual practices remain a major contributor to global morbidity, premature mortality, and health care burden. More than 1 million people acquire a sexually transmitted infection (STI) daily, including HIV. Although biomedical innovations such as pre-exposure prophylaxis have expanded prevention options, consistent condom use and regular HIV and STI testing remain essential behavioral strategies. Adherence to these behaviors remains uneven, underscoring the need for complementary digital and behavioral approaches. Digital behavior change interventions (DBCIs), technology-based programs designed to support health-related behavior change, offer scalable and personalized tools for safer-sex promotion. However, evidence regarding their behavioral components and effectiveness remains fragmented across systematic reviews (SRs). OBJECTIVE: This study aims to synthesize and critically appraise evidence on the effectiveness of DBCIs for preventing STIs and HIV, and to identify which behavior change techniques (BCTs) and theoretical domains framework (TDF) have been used to improve safe-sex behaviors. METHODS: A search was conducted in MEDLINE, Cochrane Database of SRs, Epistemonikos, and PsycINFO for all publications up to November 12, 2025, without language or date restrictions. Eligible SRs examined DBCIs targeting STI and HIV prevention or reduction of risky sexual behaviors. Two reviewers (GDA and DLA) independently screened, extracted data, and appraised methodological quality using the AMSTAR-2 tool. The reporting followed the PRIOR (Preferred Reporting Items for Overviews of Reviews) and PRISMA-S (Preferred Reporting Items for SRs and Meta-Analyses Literature Search Extension) recommendations. RESULTS: Overall, 23 SRs, comprising 514 primary studies and 129,481 participants, met the inclusion criteria. Most interventions were SMS-based, mobile app-based, or web-delivered. Digital interventions consistently improved STI and HIV testing uptake and engagement with sexual health services. Evidence for condom use and biological outcomes was mixed. Improvements in cognitive determinants, such as HIV-related knowledge, motivation, and self-efficacy, were frequently reported. Only 4 reviews explicitly applied BCT or TDF taxonomies, identifying goal setting, feedback on behavior, and prompts and cues as commonly used techniques. Research predominantly originated from high-income settings, with limited evidence from low- and middle-income countries and minimal reporting of sex- or gender-disaggregated outcomes. CONCLUSIONS: DBCIs show promise for strengthening STI/HIV prevention, particularly by increasing testing behaviors and supporting cognitive determinants of risk reduction. However, sustained condom use and biological outcomes remain inconsistent, and reporting of behavioral mechanisms is limited. This overview is the first to integrate effectiveness evidence with a systematic, mechanism-focused mapping of BCTs and TDF constructs, providing an innovation not present in earlier reviews. Clarifying which active components of digital interventions are most consistently linked to beneficial outcomes offers concrete guidance for designing culturally tailored, theory-driven, and equity-focused digital strategies. These insights have direct implications for researchers, clinicians, and policymakers seeking to develop digital prevention programs that more effectively address behavioral determinants of STI and HIV risk. TRIAL REGISTRATION: PROSPERO CRD42023485887; https://www.crd.york.ac.uk/PROSPERO/view/CRD42023485887. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.5867/medwave.2025.02.3020.