CrossRef

Crossref is a not-for-profit membership organization that coordinates the assignment of Digital Object Identifiers (DOIs) to scholarly content and maintains a centralized metadata database. It was established in 2000 by academic publishers to create a stable, interoperable system for linking and accessing research outputs across the web.

Publishers register DOIs with Crossref and submit metadata for each item, including title, authors, publication venue, date, and funder information. Crossref's metadata can be retrieved via its Metadata API and is used by libraries, indexing services, search engines, and funders to enable persistent linking, accurate citation, and discovery.

Beyond DOI registration, Crossref provides services that enhance scholarly links. Crossmark indicates current document status and any updates; the Funder Registry (formerly FundRef) links research outputs to funding sources; Cited-by tracks citations to Crossref-registered items; and Event Data records conference proceedings and other events.

Participation is open to publishers and other organizations involved in scholarly publishing. Members pay annual fees and per-DOI registration charges. Crossref is governed by a board and operates with transparent data practices, offering open access to metadata through its API while maintaining data quality standards.

In practice, Crossref-supported DOIs enable persistent, machine-readable links that survive changes to publisher websites. The system supports interoperability across bibliographic databases, repository systems, and discovery tools, making it a foundational component of modern scholarly infrastructure.