Background: Online sexual health services could widen access to sexual healthcare but some (e.g., those of lower digital literacy) face barriers to accessing and using them. The SEQUENCE Digital Programme (sequencedigital.org.uk) focusses on optimising and evaluating the eSexual Health Clinic (eSHC), an online, integrated system for accessing STI test results, treatment and partner notification and management. We aimed to develop evidence-andtheory- based recommendations to maximise inclusion and accessibility of the eSHC, using a qualitative research design. Methods: Using the PROGRESS+ framework to inform purposive sampling, we recruited diverse participants who had struggled to/never used online sexual health services (aged 18-70), from five publicly funded UK sexual health services and three UK community-based organisations (04.10.21- 18.03.22). We conducted semi-structured interviews exploring barriers and facilitators to getting STI results online, completing an automated online treatment consultation and accessing treatment. We used thematic analysis to identify barriers and facilitators then the Behaviour Change Wheel to develop recommendations to overcome barriers and enhance facilitators. Recommendations were developed considering Acceptability, Practicability, Effectiveness, Affordability, Side-effects, and Equity. Results: Key recommendations include: Signpost information/links to (emotional) support (e.g., live chat; support groups; short-term methods to reduce anxiety); Provide demonstrations and instructions on how to complete the online tasks (e.g., audio-visual step-by-step walk-throughs to demystify key processes); Explain the potential consequences of a positive STI result for self/others (e.g., videos of healthcare professionals/peers emphasising the consequences of the results); Highlight relative convenience and increased autonomy of online sexual healthcare (e.g., use of a decisional balance sheet to outline pros/cons); and Inform about equivalence of online and in-person sexual healthcare (e.g., embed written information that the results would be the same online as if they got them over the phone or face-to-face). These should be provided before getting results online and throughout the online pathway. Conclusion: Using a rigorous behavioural science approach, we developed simple and actionable recommendations which could be incorporated into the design and implementation of online sexual healthcare, including the eSHC, to maximise inclusivity and reduce barriers for people who might otherwise be excluded from online systems. These could play an important role in reducing health inequalities. [ABSTRACT FROM AUTHOR]