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Research Centre for Open Scholarly Metadata, University of Bologna


Launched: 2010
Record Updated: Apr 18, 2024
Open scholarly dataset
OpenCitations is an independent not-for-profit infrastructure organization for open scholarship dedicated to the publication of open bibliographic and citation data by the use of Semantic Web (Linked Data) technologies. It is also engaged in advocacy for open citations, particularly in its role as a key founding member of the Initiative for Open Citations (I4OC).


As a key infrastructure component for global Open Science, the mission of OpenCitations is to harvest and openly publish accurate and comprehensive metadata describing the world's academic publications and the scholarly citations that link them, and to preserve ongoing access to this information by secure archiving. We provide this information, both in human-readable form and in interoperable machine-readable Linked Open Data formats, under open licenses at zero cost and without restriction for third-party analysis and re-use.

Key Achievements

  1. In 2021, we crossed the threshold of one billion citations stored ingesting data from Crossref; in 2022, we extended the collection of open citations with data from two additional sources, DataCite and PubMed; and, in 2023, expanded the availability of open citation data by adding missing citations from OpenAIRE and the Japan Link Center (JaLC).
  2. We expanded our collection besides the citation data by releasing OpenCitations Meta, a database storing and delivering bibliographic metadata for all the publications in the OpenCitations Index, including the publication’s title, type, venue (e.g. journal), volume number, issue number, page numbers, publication date, identifiers and details of the main actors involved in the document’s publication (the names of the authors, editors, and publishers).
  3. In November 2023, we launched the new ingestion workflow, to produce two comprehensive collections: OpenCitations Index and OpenCitations Meta.
  4. As of December 2023, the OpenCitations Index contains information on 1.97 billion unique open citations.

Technical Attributes

Open Code Repository


Maintenance Status

Actively maintained

Technical Documentation


Open Product Roadmap


Open API


Open Data Statement


Content Licensing

The text of the web pages that comprise the OpenCitations web site is made freely available under a Creative Commons Attribution 4.0 International Public License. All our data are released using the CC0 to maximise their reuse.

Standards Employed


Hosting Options & Service Providers

Hosting Strategy

Not applicable

What other tools and projects does your project interact with?

Figshare, Internet Archive, GitHub, OpenAIRE, RISIS, EOSC, GraspOS

Community Engagement

Code of Conduct


Contribution Guidelines or Fora


Organizational Commitment to Community Engagement

Community engagement in OpenCitations has three aspects:
  • Collaborative partnerships with like-minded individuals, infrastructures, services and data providers, including involvement of third parties (for instance by university librarians) in the direct provision and curation of OpenCitations data.
  • Community crowdfunding to provide financial support for OpenCitations.
  • Community participation in the development and governance of OpenCitations, and in the provision and curation of its metadata.

Engagement with Values Frameworks

OpenCitations espouses fully the founding principles of Open Science. It complies with the FAIR data principles by Force11 that data should be findable, accessible, interoperable and re-usable, and it complies with the recommendations of I4OC that citation data in particular should be structured, separable, and open. OpenCitations embraces the Principles of Open Scholarly Infrastructure and conducted a POSI self-audit in 2021:

User Contribution Pathways

  • Contribute funds
  • Contribute to code
  • Contribute to documentation
  • Contribute to education or training
  • Contribute to working groups or interest groups

Policies & Governance

Governance Summary

For administrative convenience, OpenCitations is managed by the Research Centre for Open Scholarly Metadata at the University of Bologna. OpenCitations' governance comprises the following bodies: the Directors; the Council, comprising one delegate appointed by each OpenCitations Member; the International Advisory Board elected by the Council, to guide the future developments of OpenCitations strategically; the Management Team.


Privacy Policy


Open Data Statement


Governance Activities

In Progress

Governance Structure & Processes


Additional Information

Organizational History

OpenCitations has formally started in 2010 as a one-year project funded by JISC (with a subsequent extension), with David Shotton as director, who at that time was working in the Department of Zoology at the University of Oxford. The project was global in scope, and was designed to change the face of scientific publishing and scholarly communication, since it aimed to publish open bibliographic citation information in RDF and to make citation links as easy to traverse as Web links. The main deliverable of the project, among several outcomes, was the release of an open repository of scholarly citation data 3 described using the SPAR (Semantic Publishing and Referencing) Ontologies, and named the OpenCitations Corpus (OCC), which was initially populated with the citations from journal articles within the Open Access Subset of PubMed Central. At the end of 2015, after David Shotton had become a member of the Oxford e-Research Centre at the University of Oxford, Silvio Peroni of the University of Bologna joined OpenCitations as co-director and technical manager, with the aim of setting up a new instantiation of the Corpus based on a new metadata schema and employing several new technologies to automate the ingestion of fresh citation metadata from authoritative sources. Silvio Peroni is now a member of the Department of Classic Philology and Italian Studies at the University of Bologna, and the current instantiation of the OCC is hosted by the Department of Computer Science and Engineering at the University of Bologna. Since the beginning of July 2016 OCC has been ingesting, processing and publishing reference lists of scholarly papers available in Europe PubMed Central. Additional metadata for these citations are obtained from Crossref and (for authors) ORCID. In 2017, OpenCitations was awarded of a grant from the Alfred P. Sloan Foundation for The OpenCitations Enhancement Project. The funding was used to improve the hardware and software infrastructure for handling the data and hosting all the services OpenCitations makes available. During this period, OpenCitations has developed a number of citation indexes using the data openly available in third-party bibliographic databases. The first and largest of these is COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. In 2019, OpenCitations wa awarded of another grant from the Wellcome Trust for the Open Biomedical Citations in Context Corpus project. The aim of this project is to create a new dataset containing data for each individual in-text reference, making it possible to distinguish references that are cited only once from those that are cited multiple times, to see which references are cited together (e.g. in the same sentence), to determine in which section of the article references are cited (e.g. Introduction, Methods), and, potentially, to retrieve the function of the citation. Recently, at the end of 2019, OpenCitations has been selected by the Global Sustainability Coalition for Open Science Services (SCOSS) for their second round of crowd-funding support. They stated that OpenCitations aligns well with open science goals and is an innovative service - considering that open citation data are important to the community since they have the potential to support change in research assessment, and if successful could be a game changer by challenging established proprietary citation services. Starting in January 2020, SCOSS will invite research organizations, scholarly institutions and funders of all sizes throughout the world to contribute financially in proportion to their size and ability to sustain OpenCitations' operations over the next three years as it transitions into a global scholarly infrastructure organization with a secure financial footing. OpenCitations is currently managed by the Research Centre for Open Scholarly Metadata, an independent research centre within the University of Bologna. The Research Centre has an International Board drawn from leaders within the main bibliographic stakeholder communities of relevance (librarians, bibliometricians, academics, data service providers, etc.) who have shown past solid commitment to open scholarship. The statutes of the Research Centre will ensure that OpenCitations' original aim of free provision of open bibliographic and citation data, services and software is maintained, and that OpenCitations as an organization cannot in future be taken over or controlled by commercial interests, nor become involved in political, regulatory, legislative or financial lobbying of any kind.

Organizational Structure

Business or Ownership Model

Fiscal sponsorship (academic institution)

Full-time Staff



Primary Funding Source


Funding Needs

External financial support is required from the stakeholder community to support OpenCitations and enable it to expand its delivery of high-quality comprehensive open bibliographic and citation metadata. Community support is necessary to make it possible for OpenCitations to move from being a 'sustainable infrastructure' (in POSI terms) to being a financially sustained infrastructure upon which the global scholarly community can rely for open bibliographic and citation metadata for many years to come.