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.
Чем полезен и как работает
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.
Что внутри
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.
Доступ по API
https://api.opencitations.net/index/v2/citation-count/doi: <doi> ; citations/references endpoints
Доступ
Programmatic API access (a key may be required, see the API tag).