OpenCitations
Citation data as public infrastructure — CC0, queryable, no licence required.
At a Glance
- Publisher
- OpenCitations (University of Bologna)
- Coverage
Open bibliographic and citation indexes, including COCI and the consolidated OpenCitations Index, exposing hundreds of millions of citation links released under CC0 with REST APIs, SPARQL endpoints and full data dumps (verify current index size and constituent collections).
- Access
Free. Data is CC0, so it can be redistributed and built upon commercially without permission.
- Free alternative
- Already free — OpenAlex and Crossref provide overlapping open citation data.
- Regional
Global, dependent on which publishers deposit open references with Crossref.
Our Take
OpenCitations exists because citation counts were, for decades, a commercial asset rather than a public record, and it remains the cleanest demonstration that they don’t have to be. For bibliometrics, reproducible research-evaluation work, or anything you need to redistribute, CC0 licensing is not a detail — it’s the whole point, and it’s why OpenCitations underpins so many downstream tools. Coverage depends on publishers choosing to open their reference lists, so it is not a drop-in replacement for Web of Science or Scopus counts; expect gaps in disciplines where the big publishers still withhold references.
Power Tips
- Use the SPARQL endpoint or bulk dumps for real analysis — the REST API is for lookups, not scale.
- Compare a sample of citation counts against Scopus or Web of Science to quantify the coverage gap in your field before publishing bibliometrics.
- Because the data is CC0, you can ship derived datasets alongside your paper without a licensing review.
Alternatives & Complements
OpenAlex, Crossref, Scite, Dimensions, Semantic Scholar
Figures last verified: July 28, 2026