Crossref

Crossref is a nonprofit association of approximately 19,000 voting members made up of 6,000 societies and publishers, including both commercial and nonprofit organizations, 6,500 academic and research institutions, research funders, museums, repositories, government agencies and NGOs. Crossref includes members with varied business models, including those with both open access and subscription policies. Crossref does not provide a database of fulltext scientific content. Rather, it facilitates the links among distributed content hosted at other sites through the use of open metadata and persistent identifiers.

Crossref interlinks millions of items from a variety of content types, including journals, books, conference proceedings, research grants, working papers, technical reports, and data sets. Linked content includes materials from scientific, technical, and medical (STM), and social sciences and humanities (SSH) disciplines. Crossref's sustainability model includes an annual membership fee, a per-record registration fee, and additional service fees, while all the metadata remains open without restriction. Crossref provides the technical and business infrastructure to provide for this infrastructure using digital object identifiers (DOIs). Crossref provides a query service for its records through an open REST API and a Search form.

In addition to the technology and metadata linking scholarly objects, Crossref enables a common linking contract among its participants. Members agree to assign DOIs to their current journal content, and they also agree to link from the references of their content to the content of other publishers. This reciprocity is an important component of what makes the system work.

Non-member organizations may participate in Crossref by integrating the metadata. Such organizations include libraries, online journal hosts, linking service providers, secondary database providers, search engines, and providers of article discovery tools.

Crossref announced the adquisition of "Retraction Watch" database in September 2023 and released it as a public resource. And since January 2025 retractions and corrections are available in the Crossref REST API.

In addition to maintaining scholarly records, Crossref provides additional services such as plagiarism screening, searching by funding, and a button on article pages and PDFs to determine the status of an item, such as whether it has been corrected or retracted.

Crossmark

The Crossmark update system facilitates updates, corrections, and retractions for the scholarly community. The reader simply clicks on the Crossmark button to view status information about the document. If an update exists, the status information will include a DOI link to the statement of correction or retraction.

Crossmark provides a cross-platform way for readers to quickly discover the status of a research output along with additional metadata related to the editorial process. Crucially, the Crossmark button can also be embedded in PDFs, which means that members have a way of alerting readers to changes months or even years after it's been downloaded.Crossmark also allows publishers to link publications about a clinical trial, such as those reporting its results, to the registration for that clinical trial.