The Data Use Ontology (DUO) describes data use requirements and limitations. DUO allows to semantically tag datasets with restriction about their usage, making them discoverable automatically based on the authorization level of users, or intended usage. This resource is based on the OBO Foundry principles, and developed using the W3C Web Ontology Language. It is used in production by the European Genome-phenome Archive (EGA) at EMBL-EBI and CRG as well as the Broad Institute for the Data Use Oversight System (DUOS).