OBJECTIVES: Since 2018, Sexual Health London (SHL) has provided remote sexually transmitted infection (STI) testing services to London residents over 16 years of age. SHL was an asymptomatic screening service. In 2020, SHL widened access to non-urgent symptomatic testing. We undertook a 4-year evaluation on the uptake of SHL's online testing pathway and outcomes, including the association of positive chlamydia and gonorrhoea nucleic acid amplification test (NAAT) outcomes with user demographics and user utility. METHODS: This is a retrospective data analysis of routine SHL clinical data from 8 January 2018 to 31 March 2022 of all STI test kit orders, focusing on HIV, chlamydia and gonorrhoea outcomes. Descriptive analysis on uptake of each stage of SHL's clinical care pathway is provided, including HIV testing outcomes. Binary logistic regression was used to examine the association between SHL user-completed online consultation information, SHL uptake and chlamydia and gonorrhoea NAAT results (negative or positive). RESULTS: During the evaluation period, there were 1 476 187 orders made by 670 293 unique users. The return rate for chlamydia and gonorrhoea NAATs was 79.5% and 67.6% for HIV blood samples. The positivity rate from sufficient samples was 4.5% for chlamydia, 1.6% for gonorrhoea and 0.3% reactivity for HIV. There were increased odds of a positive chlamydia and gonorrhoea NAAT result in non-cisgender women, those with a high number of STI orders, non-UK born and those who collected an STI test kit from a clinic-based service. CONCLUSIONS: To date, this is the largest number of orders in an evaluation of online postal sexual health infection testing in the UK, and highest return rate of samples, suggesting acceptability of SHL for STI testing. Positivity rates for chlamydia and gonorrhoea NAAT tests are lower than national figures, which may reflect asymptomatic screening prior to 2020 and testing of non-urgent symptoms since 2020.