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Crossref (formerly styled CrossRef)[1] is a nonprofit open digital infrastructure organization for the global scholarly research community. It is the largest digital object identifier (DOI) Registration Agency of the International DOI Foundation. It has 19,000 members from 150 countries representing publishers, libraries, research institutions, and funders and was launched in early 2000 as a cooperative effort among publishers to enable persistent cross-platform citation linking in online academic journals.[2] As of July 2023, Crossref identifies and connects 150 million records of metadata about research objects made openly available for reuse without restriction. They facilitate an average of 1.1 billion DOI resolutions (clicks of a DOI link) every month, and they see 1 billion queries of the metadata every month.
Key Information
Background
[edit]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.[citation needed]
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.
Metadata
[edit]When a scholarly journal publishes an article, typically the publisher will enter the following information about the article into CrossRef: journal name, article DOI, publication date, journal volume, issue, and page, URL of article as well as journal, and number of pages. Optional metadata that can be entered includes the text of the article abstract, ORCID iDs of the authors, funding information, including funder registry IDs and funding award numbers, license information, and similarity check URLs.
The references cited by a work can also be added. This contributes to the Crossref Cited-by service, which allows one to see what articles have cited another.[3] Most major scholarly publishers do provide the references to each of their articles - Elsevier was a major holdout but began providing references in 2021.[4]
Crossref does not currently support adding information about the role of each author or other contributor to an article, but this feature is planned to be released in 2025, at least for CRediT information.[5]
Services
[edit]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
[edit]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.
— Crossref[6]
Crossmark also allows publishers to link publications about a clinical trial, such as those reporting its results, to the registration for that clinical trial.[7]
Challenges
[edit]In June 2024 a paper got wider audience when a team of researchers found fabricated metadata entered into the Crossref database, in the case of the analyzed publisher 9% of the references were wrong. This then also got sourced into datasets like Openalex. Metadata in the reported examples does not contain the real citations any more, but made up citations.[8][9]
Awards
[edit]In September 2012, Crossref was awarded the Association of Learned and Professional Society Publishers (ALPSP) Award for Contribution to Scholarly Publishing. According to ALPSP, "With over 4,000 participating publishers, Crossref's reach is international and it is very well regarded not just amongst publishers, but also the literary community and researchers. Crossref has built on this unique position to offer other services such as Crossref Cited by Linking, CrossCheck, CrossMark and the latest project, FundRef. Crossref's services provide solutions that are best done collectively by the industry to improve scholarly communications."[10]
The Council of Science Editors (CSE) awarded Crossref its Award for Meritorious Achievement at the CSE annual meeting in May 2009. This was only the second time the award had been presented to an organization rather than to an individual.[11]
In September 2008, ALPSP awarded Crossref its Innovation in Publishing award for the CrossCheck plagiarism screening service powered by iThenticate.[12] In 2025, to mark the organisation's 25th anniversary, they launched their own Crossref Metadata Awards to emphasize their community’s role in stewarding and enriching the scholarly record.[13] The six winners selected on the basis of the overall highest coverage of metadata elements included in Participation Reports.[14]
See also
[edit]References
[edit]- ^ Hendricks, Ginny (2015-11-11). "The logo has landed". Crossref Blog. doi:10.64000/ggwer-c7839. Archived from the original on 2023-02-14. Retrieved 2016-05-02.
{{cite journal}}: CS1 maint: bot: original URL status unknown (link) - ^ "History/mission". Crossref.org. PILA Inc. Retrieved 2021-07-21.
- ^ Bartell, Amanda. "Cited-by". Crossref. Retrieved 2024-12-24.
- ^ "Q&A about Elsevier's decision to open its citations". www.leidenmadtrics.nl. 2020-12-22. Retrieved 2024-12-24.
- ^ "CRediT taxonomy/author contribution". Crossref community forum. 2024-05-29. Retrieved 2024-12-24.
- ^ "About Crossmark". Crossref. Retrieved 2023-07-21.
- ^ Bartell, Amanda. "Clinical trial data and articles linked for the first time". Crossref. doi:10.64000/t2fmq-vdb52. Retrieved 2025-01-01.
- ^ Besançon, Lonni; Cabanac, Guillaume; Labbé, Cyril; Magazinov, Alexander (2024-05-06). "Sneaked references: Fabricated reference metadata distort citation counts". Journal of the Association for Information Science and Technology. 75 (12): 1368–1379. arXiv:2310.02192. doi:10.1002/asi.24896. ISSN 2330-1635.
- ^ "Hacking Scientific Citations - Schneier on Security". www.schneier.com. 15 July 2024. Retrieved 2024-07-17.
- ^ "ALPSP announces Winners of the 2012 Awards". ALPSP Web site. ALPSP. Archived from the original on 2013-06-20. Retrieved 2014-04-05.
- ^ Bradford, Monica (October 2009). "CSE Award for Meritorious Achievement: Presentation to CrossRef" (PDF). Science Editor. 32 (5). Council of Science Editors: 147. Archived from the original (PDF) on 2021-11-04. Retrieved 2016-05-01.
- ^ Brand, Amy. "CrossCheck Wins 2008 ALPSP Award for Publishing Innovation". Crossref Blog. Crossref. Archived from the original on 2015-09-23. Retrieved 2014-04-05.
- ^ Rosa-Clark. "Meet six winners of the first ever Crossref Metadata Awards". Crossref. doi:10.64000/xh94q-w7335. Retrieved 2025-07-09.
- ^ "Crossref announces inaugural Metadata Awards". Research Information. 2025-05-07. Retrieved 2025-07-09.
External links
[edit]
Wikidata has the property:
- Official website
- Crossref Blog Archived 2015-11-14 at the Wayback Machine
Crossref
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History and Background
Founding and Early Years
The development of the Digital Object Identifier (DOI) system, a precursor to Crossref, began in 1996 when the Enabling Technologies Committee of the Association of American Publishers issued a request for proposals for a persistent identifier system to manage digital content and protect intellectual property. The Corporation for National Research Initiatives (CNRI) proposed its Handle System, which was selected and prototyped to enable unique, location-independent identification of digital objects. This laid the technological foundation for linking scholarly publications reliably across the web.[7][2] In 1998, the International DOI Foundation (IDF) was established as a not-for-profit organization to develop, maintain, and govern the DOI system, building on the Handle System and addressing the needs of the publishing community for standardized intellectual property management in the digital environment. The IDF collaborated with initiatives like the INDECS project (1998–2000) to refine the DOI's data model and syntax, ensuring interoperability for content identification. By 1999, these efforts had progressed to practical applications in scholarly linking.[7][8] A key milestone occurred in 1999 with the DOI-X prototype project, led by Academic Press and Wiley in partnership with the IDF, which demonstrated automated reference linking using DOIs and a centralized metadata database. The prototype was showcased at the Frankfurt Book Fair in October 1999 during the STM Annual Conference, impressing representatives from major publishers and prompting a coalition. In December 1999, 12 founding organizations—including the American Association for the Advancement of Science, Academic Press, American Institute of Physics, Association for Computing Machinery, Blackwell, Elsevier Science, Institute of Electrical and Electronics Engineers, Kluwer Academic Publishers, Macmillan Magazines (Nature), Oxford University Press, Springer-Verlag, and John Wiley & Sons—committed to creating a dedicated linking service.[7][9][2] Crossref was incorporated on January 27, 2000, as Publishers International Linking Association, Inc. (PILA), a not-for-profit entity based in New York to operate the service independently. The system launched on June 5, 2000, as the first collaborative reference linking network for scholarly journals, initially enabling links across over 1.3 million articles from 2,700 journals submitted by 33 publishers. Ed Pentz, who had experience in electronic publishing from launching Academic Press's first online journal in 1995, was appointed as the founding Executive Director on February 1, 2000, overseeing the launch and focusing on persistent citation linking among member publishers to enhance research discoverability.[7][10][11]Growth and Key Milestones
Crossref marked its 10th anniversary in 2009 by commissioning and publishing The Formation of Crossref: A Short History, a document reflecting on its origins and early development as a collaborative infrastructure for scholarly linking.[2] Since its inception with 12 founding publisher members in 2000, Crossref has expanded dramatically, growing to over 23,000 members spanning more than 160 countries by 2025.[1] This growth reflects a broadening scope beyond traditional publishers to encompass a diverse array of institutions, funders, and research organizations, fostering a more inclusive ecosystem for scholarly communication. In 2025, marking its 25th anniversary, Crossref launched the Metadata Awards to recognize community efforts in metadata quality. Headquartered in Lynnfield, Massachusetts, Crossref has evolved into a global not-for-profit entity supporting open infrastructure for research outputs.[1][12][13] Key milestones underscore this expansion. By early 2024, Crossref had amassed over 170 million metadata records, building on earlier achievements such as reaching 100 million records around 2019 and surpassing 150 million by mid-2023. As of November 2025, this figure stands at over 176 million, accompanied by robust usage metrics including approximately 1.1 billion monthly DOI resolutions and over 2 billion metadata queries.[1][14][4] These scales highlight Crossref's role in enabling persistent access to scholarly content worldwide. Financially, Crossref has sustained steady operations, reporting a budget of around USD $13 million in revenue as of 2025.[15] Operationally, the organization has scaled its team from a single employee in 2000 to 49 staff members by 2025, supporting enhanced technological capabilities and community engagement.[1]Organization and Governance
Structure and Leadership
Crossref operates as a nonprofit organization under the legal entity Publishers International Linking Association, Inc. (PILA), registered in New York, USA, with 501(c)(6) tax-exempt status.[16] It follows a community-governed model, where a board of directors, elected by members, oversees strategic direction, operations, budget approvals, and bylaw amendments, ensuring alignment with its mission to facilitate scholarly communication.[16] The board meets quarterly to make key decisions through motions, promoting open governance and collective input from various committees representing the global research community.[16] Leadership at Crossref is headed by Executive Director Ed Pentz, who founded the organization in 2000 and continues in this role, guiding day-to-day operations and long-term vision.[1] The current Chair of the board is Lisa Schiff from the California Digital Library, supported by a Treasurer (Rose L’Huillier from Elsevier) and Secretary (Lucy Ofiesh, Crossref's Chief Operating Officer).[17][16] The board comprises 16 members drawn from diverse sectors, including academic publishers, learned societies, libraries, research funders, and technology organizations, with representation from multiple countries to reflect the international scope of scholarly publishing.[16] This composition emphasizes inclusive decision-making, with terms typically lasting three years and elections held annually to renew approximately one-third of the seats.[18] Operationally, Crossref maintains a distributed team of 49 people as of 2025, focused on sustaining core infrastructure, developing tools and services for metadata management, and providing support to its member community worldwide.[1] The organization's financial model relies primarily on tiered annual membership fees, which fund operations and are scaled according to members' publishing revenue or expenses, supplemented by fees for content registration services.[19] Transparency is ensured through publicly available annual reports detailing revenue, expenditures, and sustainability efforts.[20]Membership and Community Involvement
Crossref's membership comprises over 23,000 organizations from more than 160 countries, encompassing publishers, research institutions, government agencies, research funders, museums, and other entities involved in scholarly communication.[21] This diverse community reflects the global scope of the organization, with members contributing to the registration and linking of over 170 million research objects as of 2025.[1] Membership requires organizations to agree to Crossref's terms, which include depositing metadata for registered content and adhering to standards for persistent identifiers. Fees are structured on a tiered basis according to an organization's annual revenue or expenses, typically tied to publication output, with annual membership fees starting from $200 for the smallest entities (revenue/expenses under $1,000 USD) and scaling up for larger publishers; additionally, a one-time deposit fee applies per new DOI or metadata record.[19] In return, members gain access to core services such as DOI registration for ensuring long-term accessibility of content, metadata deposition to enhance discoverability, and utilization of tools like Crossmark for signaling updates and Similarity Check for plagiarism detection.[21] The Global Equitable Membership program further supports participation by waiving fees for organizations in least economically advantaged countries, promoting inclusivity in scholarly infrastructure.[22] The Crossref community fosters active engagement through various collaborative mechanisms, including working groups that advise on technical and policy developments, and an online forum where members discuss implementation challenges and share best practices.[23] Regular events, such as the Crossref Community Update held on May 7, 2025, provide opportunities for feedback on initiatives like the metadata schema version 5.4 update, which introduced enhancements for citations and abstracts.[24] Collaborative projects, exemplified by the first Metadata Sprint in April 2025 in Madrid, Spain, bring together participants to address specific metadata improvement tasks, strengthening community ties and advancing shared goals.[25] Members play a pivotal role in the sustainability of Crossref by collectively funding and governing the infrastructure that stewards the scholarly record, ensuring equitable access to research outputs worldwide through metadata exchange and persistent linking.[1] This shared model, sustained by membership contributions, supports over 2 billion monthly API queries and promotes the long-term integrity of global research dissemination.[26]Core Infrastructure
DOI Registration and Persistent Linking
Crossref operates as the largest Digital Object Identifier (DOI) Registration Agency (RA) under the governance of the International DOI Foundation (IDF), which oversees the DOI system as defined in ISO 26324. With over 23,000 members from more than 160 countries, Crossref manages more than 170 million DOI records, far surpassing other RAs in scale and global reach. This infrastructure supports the scholarly community by providing persistent identifiers that ensure long-term accessibility to research outputs, regardless of changes in hosting or location.[1][27] The DOI registration process begins with membership, where organizations obtain a unique DOI prefix from Crossref. Members then construct DOIs by appending a suffix to this prefix and deposit associated metadata in XML format using Crossref's schema, either through automated systems or manual interfaces. This applies to a wide range of content types, including journal articles, books and chapters, conference proceedings, datasets, dissertations, preprints, reports, and standards. Once registered, the DOI serves as a permanent handle, resolving to the current location of the content via the Handle System managed by the Corporation for National Research Initiatives (CNRI). Crossref facilitates approximately 1.3 billion successful DOI resolutions monthly, accounting for 94% of all global DOI activity and enabling seamless access to scholarly materials.[28][29][30] Reference linking forms a core component of Crossref's functionality, allowing automated matching of citations in reference lists to corresponding DOIs across publications. Members are required to include DOIs in their outgoing references and accept incoming links, with Crossref providing free tools to parse and match unstructured citations to registered metadata. This process enhances interoperability by eliminating the need for bilateral agreements between publishers, fostering a interconnected web of scholarly content where users can navigate from one full-text source to another with a single click. For instance, a citation in a journal article can resolve directly to the DOI of the referenced work, regardless of the publisher.[31][32] Crossref's DOI system integrates with global research infrastructure to support non-traditional outputs, extending beyond conventional publications. Members can register DOIs for preprints, with around 16,000 new preprint DOIs added monthly since schema support was introduced in 2016, enabling early citation and versioning. Similarly, DOIs are assigned to software and datasets, often through collaborations like those with DataCite, allowing publications to link bidirectionally to these resources and promoting reuse in computational and data-driven scholarship. This broad applicability ensures that diverse outputs, such as code repositories or data collections, remain persistently discoverable within the scholarly ecosystem.[33][34][35]Metadata Standards and Schema
Crossref maintains a structured metadata schema to ensure consistency and interoperability for scholarly content registered with digital object identifiers (DOIs). The schema defines required, recommended, and optional elements that capture essential details about research outputs, including DOIs as unique identifiers, titles, contributor information (such as authors with integrated ORCID iDs for persistent identification), abstracts, funding details, and references to support citation tracking.[36][37][38] As of 2025, Crossref has amassed over 170 million open metadata records, enabling widespread reuse in discovery tools and analyses.[1] The metadata deposit schema has evolved to accommodate richer descriptions, with version 5.4.0 released in March 2025 introducing support for multiple contributor roles (including "corresponding author" and "other"), a type attribute for citations to improve matching, version numbering for works, and expanded language options.[39][40] These updates build on prior versions by enhancing the granularity of roles and references, which facilitate the construction of comprehensive citation graphs across scholarly literature.[41] Full integration of the CRediT taxonomy for detailed contributor roles is planned for subsequent schema releases, such as version 5.5, to further standardize acknowledgments of diverse contributions.[42][43] Members deposit metadata primarily through XML files formatted according to the Crossref schema, submitted via HTTPS POST or the web-based admin tool, which supports uploads of XML built to standards like NLM or JATS.[44][45] The process emphasizes depositing rich, structured data—such as full references and funding awards—to maximize discoverability, interoperability, and reuse in global scholarly ecosystems.[46][47] All deposited metadata is publicly accessible without restriction, supporting nearly 2 billion monthly API queries as of 2025 to power tools like search engines and reference managers.[48] Retrieval occurs via the REST API, which provides metadata in JSON or XML formats, alongside OAI-PMH and other interfaces; rate limits for public and polite pools will be revised starting December 1, 2025, to sustain performance amid growing demand.[49][50] This open access model underpins Crossref's role in fostering a connected research infrastructure.[1]Services and Tools
Crossmark and Content Updates
Crossmark is a service provided by Crossref that enables the display of post-publication updates for scholarly content associated with Digital Object Identifiers (DOIs). Launched on April 27, 2012, it aims to alert readers to important changes such as corrections, retractions, and version updates, while also providing access to additional editorial metadata like publication history and licenses.[51][52] The functionality of Crossmark relies on participating publishers depositing specific metadata through Crossref's DOI registration system. When an update occurs, members submit details including the type of change (e.g., correction or retraction) and a link to the updated content, which Crossref stores and makes accessible via an API. Readers encounter a Crossmark button or badge embedded on the publisher's website or PDF near the content's title; clicking it reveals a pop-up dialog showing the current status—such as "up-to-date," "updated," or "retracted"—along with timestamps, descriptions of changes, and links to the latest version. This system supports tracking retractions by flagging affected DOIs, ensuring the scholarly record remains transparent without altering the original publication.[52][53] By facilitating easy visibility of post-publication modifications, Crossmark enhances trust in the integrity of scholarly outputs, allowing researchers, librarians, and readers to verify the currency and reliability of cited works. For publishers, it demonstrates a commitment to maintaining the scholarly record, potentially increasing the perceived credibility of their content and enabling the sharing of supplementary information like peer-review status or funding details. Integration with major platforms, including support for REST API queries, further streamlines its use across diverse publishing workflows.[52][54] Adoption of Crossmark has grown steadily among Crossref members, with participation becoming a standard practice for many large publishers to signal ongoing maintenance of their outputs. As of March 2020, 440 Crossref members had implemented the service, registering Crossmark metadata for 11.4 million DOIs, including notable examples from Elsevier, Oxford University Press, and the Royal Society. While not mandatory for all members, it is required for those opting into the service to apply the badge consistently to new content and maintain a policy page outlining update procedures, with backfile application encouraged but optional. Early adopters in 2012 included 21 journals covering nearly 20,000 documents, marking initial traction for retraction and update tracking.[54][51][53]Cited-by Linking and Similarity Check
Crossref's Cited-by service enables publishers to discover and display forward citations to their content, fostering connections between scholarly works. Launched in early 2021 with significant expansion following Elsevier's decision to open its reference data, the service now covers over 90% of Crossref's registered DOIs, allowing members to retrieve comprehensive lists of citing articles, including citation counts and direct links to the citing works.[55][56] This functionality relies on members depositing reference lists as part of their DOI metadata submissions, which are then parsed to create accurate citation links across the ecosystem.[57] The service provides public API endpoints for accessing citation metrics, such as the total number of citing works via the"is-referenced-by-count" field in metadata responses, enabling integration into publisher websites and research assessment tools. For instance, scholars can query citations for a specific DOI to explore how ideas evolve through subsequent research, enhancing discoverability without additional costs to participants.[58] Non-participating members risk underreporting citations by up to 20%, underscoring the value of comprehensive reference deposition.[55]
Complementing citation tracking, Crossref's Similarity Check service—formerly known as CrossCheck—supports content integrity by detecting potential plagiarism in manuscripts before publication. Powered by iThenticate software from Turnitin, it scans submitted texts against a vast database exceeding 78 million scholarly publications and web sources, generating an originality report with similarity scores and highlighted matches.[59][60] Eligible Crossref members, who must include full-text URLs in at least 90% of their metadata deposits, gain discounted access to upload unlimited manuscripts for analysis.[61] This pre-publication screening helps editors verify originality, protects publication reputations, and educates authors on proper citation practices.[62]
Implementation of both services integrates seamlessly with Crossref's core infrastructure, where reference metadata deposition underpins Cited-by links, while full-text accessibility enables Similarity Check comparisons. Their combined impact bolsters research assessment by providing reliable citation networks and ensuring ethical content creation; for example, the 2024 milestone of the related Grant Linking System registered over 125,000 grants, facilitating traceable funding-to-output connections that enhance transparency in scholarly evaluation.[63]