scholarly-metadata
OpenCitations
An open index of scholarly citation links, with more than two billion DOI-to-DOI connections as of its February 2026 refresh. Citation counts, incoming citations, and reference lists for any DOI are available through a free API; the website's search page sits behind a CAPTCHA, but the API answers cleanly. Use it to see who cites a paper or to build citation trails from fully open data.
Son utilité et son fonctionnement
OpenCitations is the primary open, freely reusable source for citation link data. Use it to retrieve citation counts, the full list of papers that cite a given work, or the references a paper makes, all identified by DOI. Because the data is fully open and the API requires no key, it is reliable for systematic citation-trail work at scale. The website's search page requires completing a CAPTCHA, but the API itself answers all queries cleanly. Citation counts and incoming-citation lists are the most common use cases.
Ce qu’elle contient
More than 2.2 billion DOI-to-DOI citation links as of the July 2025 data dump, drawn from open references deposited with Crossref and DataCite and refreshed several times per year.
Accès API
https://api.opencitations.net/index/v2/citation-count/doi: <doi> ; citations/references endpoints
Accès
Programmatic API access (a key may be required, see the API tag).