VI · 40
OpenURL & Crossref
Crossref runs an OpenURL endpoint that returns rich citation metadata for a DOI or descriptive query, used by hundreds of citation tools.
Crossref, the largest DOI registration agency, operates an OpenURL endpoint at doi.crossref.org/openurl. The endpoint accepts OpenURL-syntax requests and returns metadata about the registered DOI matching the request. It is widely used by citation managers, indexers, and discovery systems to fetch metadata for a known DOI or to match descriptive metadata to a DOI.
Endpoint
https://doi.crossref.org/openurl
Requests are HTTP GET. Most callers send standard OpenURL parameters, sometimes mixed with Crossref-specific options.
Common parameters
| Parameter | Purpose |
|---|---|
pid | Required identification — typically the caller's email address, used by Crossref for rate-limit accounting. |
id | DOI lookup. The value may be a bare DOI or in the form doi:<DOI>. |
noredirect | If true, return metadata rather than redirecting. |
format | Response format: unixsd (modern Crossref schema) or unixref (legacy schema). |
rft_id | Standard OpenURL identifier carrying info:doi/<DOI>. |
rft.* | Standard OpenURL descriptors — Crossref will attempt to match descriptive metadata to a registered DOI. |
Example request
A descriptive-metadata lookup, asking for the unixsd-format response:
https://doi.crossref.org/openurl?
pid=your-email%40example.org
&rft.atitle=Can+Quantum-Mechanical+Description+of+Physical+Reality+Be+Considered+Complete%3F
&rft.aulast=Einstein
&rft.jtitle=Physical+Review
&rft.date=1935
&rft.volume=47
&rft.spage=777
&noredirect=true
&format=unixsdA DOI lookup:
https://doi.crossref.org/openurl?
pid=your-email%40example.org
&id=doi:10.1103/PhysRev.47.777
&noredirect=true
&format=unixsdNotes
- Use a real, monitored email address in
pid. Crossref may reduce service to clients without one. - For high-volume metadata retrieval, Crossref's REST API (
api.crossref.org) is generally a better fit. The OpenURL endpoint exists primarily for compatibility with OpenURL-based citation tools. - Crossref's OpenURL endpoint is documented at the URL listed in the Sources section below.