Clarivate’s Highly Cited Researchers (HCR) list is one of the most important quantitative performance indicators in science and influences individual careers and also the reputation of research institutions. However, many researchers and representatives of institutions and funding agencies are not familiar with the method that is applied to generate the HCR lists. We therefore provide a detailed description of Clarivate’s method and give an example to illustrate how HCR are identified. While Clarivate provides the complete HCR lists and a detailed description of the method used for identifying HCR, the detailed analysis with actual numbers is not published. It is therefore not entirely transparent how exactly the HCR were identified, and which authors were excluded from the initial list, e.g. due to scientific misconduct. It is also impossible to check the analysis for errors. Given the prestige and weight that is attributed to Clarivate’s HCR list, we call for transparency of the data and analysis behind the HCR list.