Worldwide, people acquire more than 1 million curable sexually transmitted infections (STIs) every day. Based on prevalence data from 2009 to 2016, in 2019, WHO published estimates of new cases of chlamydia, gonorrhoea, syphilis and trichomoniasis, showing total estimated incident cases of 376.4 million among people 15–49 years old in 2016, with 127.2 million new cases of chlamydia, 86.9 million new cases of gonorrhoea, 156 million new cases of trichomoniasis and 6.3 million new cases of syphilis. The prevalence of some viral STIs is similarly high, with an estimated 417 million people infected with herpes simplex virus type 2 (HSV-2) and about 291 million women harbouring human papillomavirus (HPV) at any point in time. The WHO global health sector strategy on sexually transmitted infections, 2016–2021, endorsed by the World Health Assembly in 2016, aims to eliminate STIs as a public health threat by 2030. The key pillars to eliminate STIs are to prevent people from being infected and to provide treatment and care for infected people to avoid further transmitting STIs to other people. The strategy makes a strong case for expanding the provision of high-quality STI prevention and care more widely into the areas of primary health care, sexual and reproductive health and HIV prevention and care services. Efforts should therefore be made to strengthen STI case management that ensures the widest possible access to high-quality services at the population level based on simplified and standardized interventions and services that can readily be taken to scale, especially in resource-limited settings. Since the WHO guidelines for the management of sexually transmitted infections were published in 2003, changes in the epidemiology of STIs and progress in prevention, diagnosis and treatment of STIs and HIV have necessitated changes in approaches to STI prevention and management. Syndromic management is widely used to manage people with symptoms of STIs. In most resource-limited settings, the syndromic management flow charts are still the standard of care where laboratory diagnosis is not available or, where it is available, getting results take several days. Although the STI syndromic approach has some shortcomings, it remains an essential component of managing people with symptoms of STIs. These guidelines aim to raise the quality of managing symptomatic STIs by providing evidence-informed recommendations. In addition, given the existence of rapid diagnostic tests that have recently become available, these guidelines also provide guidance on how to use them in settings in which they are accessible.