Since Bohan-Peter criteria, several classification criteria for idiopathic inflammatory myopathies (IIM) have been proposed reflecting the advancements in understanding of these diseases over the years. This created a strong foundation for development of the first data-derived IIM criteria. Since its publication in 2017, European Alliance of Associations for Rheumatology (EULAR)-American College of Rheumatology (ACR) IIM criteria have been widely used in studies, demonstrating good performance across various populations. However, the emergence of new IIM subtypes and advancements in diagnostics have exposed gaps in the criteria, necessitating a revision. This article summarizes the historical evolution of the IIM classification criteria and outlines the key reasons for revision of the EULAR-ACR criteria.