The Clusters of Orthologous Groups (COGs) database, a popular tool for functional annotation of microbial genomes, has been updated to include representative complete genomes from all bacterial and archaeal lineages down to the genus level. This update, the first since 2003, aims to improve the accuracy and coverage of protein function annotations. The new version of COGs includes 711 genomes, representing a wide range of microbial diversity, and re-evaluates the annotations of over half of the COGs, leading to name changes for many entries. The annotations have been verified against various databases and curated to ensure accuracy and consistency. The update highlights the progress in functional genomics over the past 12 years, with many previously uncharacterized COGs now assigned functions, particularly in translation processes such as rRNA maturation and tRNA modification. The revised COGs are expected to become an important resource for microbial genomics, facilitating more accurate and straightforward annotation of new genomes.The Clusters of Orthologous Groups (COGs) database, a popular tool for functional annotation of microbial genomes, has been updated to include representative complete genomes from all bacterial and archaeal lineages down to the genus level. This update, the first since 2003, aims to improve the accuracy and coverage of protein function annotations. The new version of COGs includes 711 genomes, representing a wide range of microbial diversity, and re-evaluates the annotations of over half of the COGs, leading to name changes for many entries. The annotations have been verified against various databases and curated to ensure accuracy and consistency. The update highlights the progress in functional genomics over the past 12 years, with many previously uncharacterized COGs now assigned functions, particularly in translation processes such as rRNA maturation and tRNA modification. The revised COGs are expected to become an important resource for microbial genomics, facilitating more accurate and straightforward annotation of new genomes.