Search papers and analyze citation graphs via OpenAlex and CrossRef APIs
OpenAlex is a free, open catalog of the global research system, indexing over 250 million academic works across all fields of science. It provides structured access to papers, authors, institutions, concepts, and citation networks. OpenAlex is the successor to Microsoft Academic Graph and is maintained by OurResearch (the team behind Unpaywall).
CrossRef is the official DOI registration agency for scholarly content, providing metadata for over 150 million DOIs across all publishers and disciplines. Together, OpenAlex and CrossRef provide comprehensive coverage for academic search, citation analysis, and bibliometric research.
Both APIs are free to use without authentication. OpenAlex requests a polite User-Agent header; CrossRef requests a User-Agent with contact email for access to the polite pool (faster rate limits).
No authentication is required for either API.
OpenAlex: Include a User-Agent header for polite access:
User-Agent: ResearchPlugins/1.0 (https://wentor.ai)
CrossRef: Include a User-Agent header with contact email for polite pool:
User-Agent: ResearchPlugins/1.0 (https://wentor.ai; mailto:[email protected])
GET https://api.openalex.org/works| Param | Type | Required | Description |
|---|---|---|---|
| search | string | No | Full-text search query |
| filter | string | No | Filter expression (e.g., from_publication_date:2024-01-01) |
| sort | string | No | Sort field (e.g., cited_by_count:desc, publication_date:desc) |
| per_page | integer | No | Results per page (default: 25, max: 200) |
| page | integer | No | Page number (default: 1) |
curl "https://api.openalex.org/works?search=attention+is+all+you+need&per_page=5"
meta (count, page info) and results array containing work objects.GET https://api.openalex.org/works/{id}| Param | Type | Required | Description |
|---|---|---|---|
| id | string | Yes | OpenAlex ID (e.g., W2741809807), DOI URL, or other identifier |
curl "https://api.openalex.org/works/W2741809807"
id, title, abstract_inverted_index, publication_year, cited_by_count, authorships, concepts, referenced_works.GET https://api.openalex.org/authors| Param | Type | Required | Description |
|---|---|---|---|
| search | string | No | Author name search |
| filter | string | No | Filter expression |
| per_page | integer | No | Results per page (max: 200) |
curl "https://api.openalex.org/authors?search=Yoshua+Bengio&per_page=5"
works_count, cited_by_count, summary_stats.h_index, affiliations.GET https://api.crossref.org/works/{doi}| Param | Type | Required | Description |
|---|---|---|---|
| doi | string | Yes | DOI to resolve (e.g., 10.1038/nature12373) |
curl "https://api.crossref.org/works/10.18653/v1/N19-1423"
OpenAlex: No strict rate limit, but use polite User-Agent header. Recommended: max 10 requests per second. The API returns HTTP 429 when limits are exceeded.
CrossRef: Without polite pool: ~50 requests per second. With polite pool (contact email in User-Agent): higher limits. The API returns HTTP 429 when limits are exceeded.
Retrieve a paper and find all works that cite it:
# Get paper details
curl "https://api.openalex.org/works/W2741809807"
# Get works citing this paper, sorted by citation count
curl "https://api.openalex.org/works?filter=cites:W2741809807&sort=cited_by_count:desc&per_page=20"
Search for highly cited works on a topic:
curl "https://api.openalex.org/works?search=graph+neural+networks&sort=cited_by_count:desc&per_page=20"
Search CrossRef for papers matching a query, sorted by citation count:
curl "https://api.crossref.org/works?query=graph+neural+networks&sort=is-referenced-by-count&order=desc&rows=20"