OpenCitations
FreeLiveLast verified 28 Sept 2026
Open scholarly citation links: references and citing works for a DOI, PMID or OMID, as JSON or CSV.
Example request
curl -s 'https://api.opencitations.net/index/v2/references/doi:10.1186/1756-8722-6-59'
Free tier, in plain English
Free with no key, up to 180 calls a minute per IP. An optional free access token is requested for apps; bulk needs should use the dumps.
Alternatives in Academic
arXivSearches and retrieves metadata for millions of physics, math, CS and related research preprints.FreeCORESearch and metadata for 200M+ open-access research papers aggregated from repositories worldwide.FreemiumCrossref Metadata SearchSearch and fetch metadata for scholarly works by DOI, title, author, funder, or journal.FreemiumEPO Open Patent ServicesSearch European and worldwide patent bibliographic, full-text and legal-status data from the EPO.FreeEurope PMCSearch abstracts and full text of biomedical and life-science research literature.Free
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