Crossref

Crossref is a nonprofit registration agency for the Digital Object Identifier (DOI) system, focused on the scholarly literature. It was founded in 2000 by a group of academic publishers to solve the problem of reciprocal reference linking: instead of every journal maintaining its own link tables, members deposit metadata for each article they publish and in return get persistent links to articles published by others. Members deposit a metadata record for each work alongside its DOI, including title, authors, journal or book, publication date, abstract, references, funders, and optionally ORCID iDs for authors. Crossref operates a free open REST API that returns this metadata, which is used by search engines, reference managers, indexing services, and research analytics tools. Additional services include Crossmark, which lets readers see if an article has been corrected or retracted; Similarity Check for plagiarism screening; and a Cited-by service that exposes inbound citations. By the mid-2020s Crossref had roughly 19,000 voting members across more than 160 countries, covered around 150 million metadata records, and handled on the order of one billion DOI resolutions per month. It is funded by membership and per-record fees, but the metadata it stewards is openly available under permissive terms, which has made Crossref central to open infrastructure efforts in scholarly publishing.