Examples
Worked examples
- Is an instance
A metadata-matching tool sends a GET request to api.crossref.org/works?query.bibliographic= &[email protected] to resolve a loosely formatted citation string to a DOI and full Crossref metadata record, receiving the polite-pool response speed because a contact mailto parameter was supplied.
Counter-examples
Looks similar, but isn't
- Not an instance
Fetching a single known DOI's citation in a specific format -- for example, BibTeX -- does not require the general /works search route at all: Crossref exposes that directly via a content-negotiation-style transform endpoint, api.crossref.org/works/{doi}/transform/application/x-bibtex, a narrower and more direct call than a bibliographic query.
Editorial commentary
The Crossref REST API is the programmatic counterpart to Crossref’s public DOI metadata search — the same free-text matching available at search.crossref.org is exposed as a queryable API, plus routes for journals, funders, members, licenses, prefixes, and content types.
Core routes
- /works — the primary metadata route; supports
query.bibliographic(free-text matching across titles, authors, ISSNs, and years, replacing the now-deprecatedquery.titleparameter), filtering, and direct DOI lookup at/works/{doi}. - /journals, /funders, /members, /licenses, /prefixes, /types — narrower routes for the corresponding metadata categories.
- Format transforms — e.g.
/works/{doi}/transform/application/x-bibtexfor a direct BibTeX record of a known DOI, an alternative to the content-negotiation route via doi.org itself.
Authentication and the polite pool
No authentication or API key is required. Including a mailto query parameter, or a User-Agent header that identifies the calling tool and a contact email, routes requests to Crossref’s “polite pool” — a set of API machines reserved for identified, well-behaved callers — since this only applies over HTTPS. Response headers include rate-limit information (x-rate-limit-limit, x-rate-limit-interval).
Frequently Asked Questions
Do I need a Crossref account to use the REST API?
No — read access to metadata via api.crossref.org requires no account or key. Depositing or updating metadata (the separate deposit/registration workflow) does require a Crossref member account and credentials.
Does the REST API cover DOIs registered by DataCite instead of Crossref?
No — api.crossref.org only indexes DOIs Crossref itself has registered. DataCite-registered DOIs (common for datasets and software) are queried via DataCite’s own separate API.
Machine-readable encodings
Use in your systems
<role vocab="credit"
vocab-identifier="https://casrai.org/dictionary/"
vocab-term="Crossref REST API"
vocab-term-identifier="https://casrai.org/dictionary/term/crossref-rest-api" />{
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"description": "The Crossref REST API (api.crossref.org) is Crossref's free, public web API for programmatically querying its registered scholarly-metadata database. It exposes routes for works, journals, members, funders, licenses, prefixes, and types, returning structured JSON that can be filtered and queried -- including free-text bibliographic matching via the query.bibliographic parameter on the /works route -- without requiring authentication, though including a mailto contact parameter or identifying User-Agent header routes requests to Crossref's faster 'polite pool.'",
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"license": "https://creativecommons.org/licenses/by/4.0/",
"publisher": {
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},
"author": {
"@id": "https://casrai.org/#editorial-team"
},
"datePublished": "2026-08-22T10:45:14",
"dateModified": "2026-09-05T17:43:46",
"inLanguage": "en-GB",
"isAccessibleForFree": true
}
