Finding Open Access Papers

Finding Open Access Papers

Overview

Use Unpaywall to find legally available open access versions of papers that appear to be behind paywalls.

Core principle: Many paywalled papers have free versions (preprints, author manuscripts, institutional repositories). Unpaywall finds them.

When to Use

Use this skill when:

• DOI resolution hits a paywall
• Paper not available in PubMed Central
• Publisher site requires subscription
• Need full text for highly relevant paper (score ≥7)

Use BEFORE giving up on full text access

Unpaywall API

Simple REST API - no authentication required for reasonable usage

Basic Request

curl "https://api.unpaywall.org/v2/DOI?email=YOUR_EMAIL"

Parameters:

• DOI - The paper's DOI (URL-encoded if needed)
• email - User's email (required, for courtesy/contact)

IMPORTANT: Ask user for their email at the start of research session. Do NOT use placeholder emails like [email protected] or [email protected].

Example:

curl "https://api.unpaywall.org/v2/10.1038/[email protected]"

Response Format

{
  "doi": "10.1038/nature12373",
  "title": "Paper Title",
  "is_oa": true,
  "best_oa_location": {
    "url": "https://europepmc.org/articles/pmc3858213",
    "url_for_pdf": "https://europepmc.org/articles/pmc3858213?pdf=render",
    "version": "publishedVersion",
    "license": "cc-by",
    "host_type": "repository"
  },
  "oa_locations": [
    {
      "url": "https://europepmc.org/articles/pmc3858213",
      "version": "publishedVersion"
    },
    {
      "url": "https://arxiv.org/abs/1234.5678",
      "version": "submittedVersion"
    }
  ]
}

Key Response Fields

is_oa (boolean)

• true - Open access version available
• false - No free version found

best_oa_location (object or null)

• Unpaywall's recommended best open access source
• Prioritizes published versions over preprints
• Includes PDF URL when available

oa_locations (array)

• All known open access locations
• Includes repositories, preprint servers, institutional sites
• Ordered by quality/version