INTRODUCTION: The new EU regulation on tattoo inks in force January 2022 in a hitherto unregulated market marks a historical change. The study aim was to register tattoo inks de facto used in studios before the new EU regulation and establish a historical reference to tattoo customer exposure, ink toxicology assessment, clinical complications, and the impact on tattooing businesses. METHOD: A tattooist-operated electronic system (InkBase) for ink registration required by law is used in Denmark since 2018. A local database in studios refers to a central database. Clients, sessions, ink bottles, brand name, and pigment color index (CI) are registered. Person's data protection is respected. Tracing harmful inks is possible, with public warning. RESULTS: Registrations from 108 studios employing about 700 tattooists were collected from March 2018 to 2019. 39,687 clients were tattooed in 50,604 sessions, using colors from 109,720 ink bottles. 10,833 were CI-labelled identifying the pigment. 98.1% of inks originated from USA. Detailed statistics on inks and pigments used are provided as a benchmark showing the spontaneous use and preference of "old" tattoo inks before the EU regulation compulsory to member states introduced dramatic restrictions difficult to follow. CONCLUSIONS: Denmark can, having detailed ink registration enforced by law and having a commonly used electronic registration system reporting to a central server, function as an index country in future surveillance of use of tattoo inks in studios, toxicology aspects and the impact of regulatory intervention on the tattooing industry, with a large sample of data collected in 2018-2019.