CrossRef API Guide

Overview

CrossRef is the official DOI registration agency for scholarly publishing, maintaining metadata for over 150 million content items including journal articles, books, conference proceedings, preprints, and datasets. The CrossRef REST API provides free, open access to this metadata, making it the authoritative source for resolving Digital Object Identifiers (DOIs) and retrieving standardized publication records.

Publishers deposit metadata with CrossRef when they register DOIs for their content. This makes the CrossRef API a reliable source for bibliographic information, citation counts, licensing data, funder acknowledgments, and links to full-text resources. The API is used extensively in reference management, citation analysis, and research information systems.

The API is free and requires no authentication. Users who include a

mailto

parameter in their requests are placed in the "polite pool" which provides faster and more reliable service.

Authentication

No authentication required. For best performance, include your email to access the polite pool:

https://api.crossref.org/works?mailto=your@email.com

Users in the polite pool receive prioritized responses and are not subject to the same rate limiting as anonymous users. CrossRef Plus subscribers get additional benefits including guaranteed uptime and higher throughput.

Core Endpoints

Works: Query Publication Metadata

• URL:

  GET https://api.crossref.org/works

• Parameters:

  Param	Type	Required	Description
  query	string	No	Free-text query across all metadata fields
  query.title	string	No	Search specifically in titles
  query.author	string	No	Search specifically by author name
  filter	string	No	Structured filters (e.g., from-pub-date:2024, type:journal-article)
  sort	string	No	Sort field: relevance, published, is-referenced-by-count
  order	string	No	asc or desc
  rows	integer	No	Results per page (default: 20, max: 1000)
  offset	integer	No	Pagination offset
  mailto	string	No	Email for polite pool

• Example:

  curl "https://api.crossref.org/works?query.title=attention+is+all+you+need&rows=5&mailto=user@example.com"
  

• Response: JSON with

  message.items

  array containing

  DOI

  ,

  title

  ,

  author

  ,

  published

  ,

  is-referenced-by-count

  ,

  reference

  ,

  license

  , and

  link

  fields.

Works by DOI: Direct DOI Resolution

• URL:

  GET https://api.crossref.org/works/{doi}

• Parameters:

  Param	Type	Required	Description
  doi	string	Yes	The DOI to resolve (URL path parameter)
  mailto	string	No	Email for polite pool

• Example:

  curl "https://api.crossref.org/works/10.1038/s41586-021-03819-2?mailto=user@example.com"
  

• Response: JSON with complete metadata record for the DOI, including all registered bibliographic information.

Members: Publisher Information

• URL:

  GET https://api.crossref.org/members

• Parameters:

  Param	Type	Required	Description
  query	string	No	Publisher name search
  rows	integer	No	Results per page

• Example:

  curl "https://api.crossref.org/members?query=springer&rows=5&mailto=user@example.com"
  

• Response: JSON with publisher metadata including member ID, name, prefix list, and coverage statistics.

Journals: Journal Metadata

• URL:

  GET https://api.crossref.org/journals

• Parameters:

  Param	Type	Required	Description
  query	string	No	Journal title search
  rows	integer	No	Results per page

• Example:

  curl "https://api.crossref.org/journals?query=nature+machine+intelligence&rows=5&mailto=user@example.com"
  

• Response: JSON with journal information including ISSN, title, publisher, subject, and coverage counts.

Rate Limits

Anonymous users: no hard limit but throttled under load. Polite pool users (with

mailto

): prioritized access with no published rate cap. CrossRef Plus subscribers: guaranteed uptime with SLA. The API returns HTTP 429 when overloaded. Use exponential backoff and always include

mailto

for production applications. For bulk metadata retrieval, CrossRef provides database snapshots and the Public Data File.

Common Patterns

Validate and Enrich a Reference List

Resolve a list of DOIs to get standardized metadata:

# Single DOI resolution with full metadata
curl "https://api.crossref.org/works/10.1145/3292500.3330672?mailto=user@example.com"

Find Recent Highly-Cited Papers in a Field

Filter by publication date and sort by citation count:

curl "https://api.crossref.org/works?filter=from-pub-date:2023,type:journal-article&query=machine+learning&sort=is-referenced-by-count&order=desc&rows=20&mailto=user@example.com"

Track Citation Growth

Monitor citation counts for a specific DOI over time:

curl "https://api.crossref.org/works/10.1038/s41586-021-03819-2?mailto=user@example.com" | jq '.message["is-referenced-by-count"]'

References

• Official documentation: https://api.crossref.org
• API documentation: https://api.crossref.org/swagger-ui/index.html
• CrossRef metadata best practices: https://www.crossref.org/documentation/