Keeps track of all historical and current miRNA annotation present in the miRBase database. Three functionalities allow researchers to keep their miRNA annotation up-to-date, reannotate analytical miRNA platforms and link published results with outdated annotation to the latest miRBase release. With a miRNA history query, the user gets an overview of the annotation changes of any mature or precursor miRNA of interest throughout the different miRBase releases. The miRBase release comparison query option compares any two miRBase releases for both mature and precursor miRNAs within any species. Users get an overview showing which miRNA records were added, removed, changed or remained unchanged, along with summarizing statistics.