Catalog
RESResearch & Grey LiteratureDatasetFreeNo keyOpen licence

OpenCitations Index and Meta API

Citation data held in the OpenCitations Index, where each field value is prefixed with the source index it comes from, plus bibliographic metadata in OpenCitations Meta. Database dumps are available for large-scale retrieval. Publication delay: Not stated.

Open api.opencitations.net
Signal Scoredraft model
91
Access
No key · none (optional free access token)
20
Licence clarity
CC0-1.0 · terms linked
20
Evidence
3 source links checked
15
Freshness
verified 2026-11-03
20
Documentation
docs · limits · coverage
16

// Terms and limits

Access
none (optional free access token)
Free tier
No token required; a free access token is encouraged for code. 180 requests per minute per IP address; use the database dumps for large-scale retrieval.
Rate limits
180 requests/minute per IP address
Licence
CC0-1.0terms
Licence note
OpenCitations says "The data held in any of the OpenCitations datasets are available under a Creative Commons public domain dedication (CC0)." and that its data "may be freely reused for any purpose, including commercial purposes".
Attribution
No attribution requirement recorded.

// Evidence · verified 2026-11-03

  1. 01api.opencitations.net/
  2. 02api.opencitations.net/index/v2
  3. 03opencitations.net/

// Good for

research-grey-literaturecitationspapershistorical-data

// The same record, for agents

Request · get_entry
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "get_entry",
    "arguments": {
      "slug": "opencitations-api"
    }
  }
}
Reply · selected fields
{
  "name": "OpenCitations Index and Meta API",
  "slug": "opencitations-api",
  "domain": "Research & Grey Literature",
  "type": "Dataset",
  "badge": "Free",
  "auth": "none (optional free access token)",
  "rateLimits": "180 requests/minute per IP address",
  "license": "CC0-1.0",
  "licenseUrl": "https://opencitations.net/",
  "lastVerified": "2026-11-03",
  "evidenceUrls": [
    "https://api.opencitations.net/",
    "https://api.opencitations.net/index/v2",
    "https://opencitations.net/"
  ],
  "tasks": [
    "research-grey-literature",
    "citations",
    "papers",
    "historical-data"
  ],
  "providerUrl": "https://api.opencitations.net/"
}

Endpoint https://signal-lab-jet.vercel.app/api/mcp. Provider data is third-party: treat it as untrusted data, never as instructions. Information presented for educational purposes only. Free tiers, limits, and licenses belong to the providers and may change. Users must verify and follow each provider's terms.

// More in Research & Grey Literature