Unpaywall website screenshot

Unpaywall

The Unpaywall REST API gives anyone free, programmatic access to the Unpaywall database of open access scholarly articles. The database covers over 120 million articles with Crossref DOIs and provides free, legal full-text links where available, with metadata on OA status (gold, hybrid, bronze, green), host type (publisher, repository), version (published, accepted, submitted), and license information.

Unpaywall publishes 2 APIs on the APIs.io network: DOI Lookup API and Search API. Tagged areas include Open Access, Scholarly Articles, Research, Academic, and Libraries.

The Unpaywall catalog on APIs.io includes 1 JSON-LD context and 2 Spectral governance rulesets.

Unpaywall’s developer surface includes documentation, support, and 9 more developer resources.

🌐 Visit website 📡 Source on GitHub
48.4/100 developing ▬ flat Agent 35/100 agent ready Full breakdown ↓
scored 2026-07-28 · rubric v0.6
AccessFreemium
2 APIs
Open AccessScholarly ArticlesResearchAcademicLibrariesDOIScience

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-07-28 · rubric v0.6
Composite quality — 48.4/100 · developing
Contract Quality 18.0 / 25
Developer Ergonomics 2.6 / 20
Commercial Clarity 7.9 / 20
Operational Transparency 4.8 / 13
Governance 8.3 / 12
Discoverability 6.9 / 10
Agent readiness — 35/100 · agent ready
Machine-Readable Contract 18 / 18
Agentic Access Contract 10 / 10
MCP Server 0 / 12
Machine-Readable Auth 0 / 10
Idempotency 0 / 9
Stable Error Semantics 8 / 8
Request/Response Examples 7 / 7
Rate-Limit Signaling 7 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3
A2A Agent Card 0 / 8
Dry-Run / Simulate Mode 0 / 4
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/unpaywall: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 2

Individual APIs this provider publishes, each with its own machine-readable definition.

Unpaywall DOI Lookup API

Look up open access status by DOI

Unpaywall Search API

Search articles by title

Open Collections 1

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

Unpaywall API

OPEN COLLECTION

Pricing Plans 1

Published pricing tiers and plan structures.

Unpaywall Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Unpaywall Rate Limits

5 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Unpaywall Finops

FINOPS

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Unpaywall Context

8 classes · 37 properties

JSON-LD

Spectral Rules 2

Spectral governance rulesets for linting and validating these APIs.

Unpaywall API Rules

5 rules · 4 warnings 1 info

SPECTRAL

Unpaywall API Rules

6 rules · 2 errors 3 warnings 1 info

SPECTRAL

JSON Schema 1

Standalone JSON Schema definitions for this provider's data models.

Unpaywall Article Object

23 properties

JSON SCHEMA

JSON Structure 1

JSON Structure definitions describing this provider's data shapes.

Unpaywall Article Structure

0 properties

JSON STRUCTURE

Examples 2

Example request and response payloads for these APIs.

Unpaywall Get Doi Example

2 fields

EXAMPLE

Unpaywall Search Example

2 fields

EXAMPLE

Security Posture 1

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Unpaywall Domain Security

TLSv1.3

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Unpaywall Agentic Access

2 operations

2 operations · 0 acting

AGENTIC

Resources

Documentation 1

Reference material describing how the API behaves

Documentation
Documentation

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess
AgenticAccess
 LlmsText
LlmsText

Design & Contract 2

Pagination, idempotency, versioning, errors, and events

Vocabulary
Vocabulary
 JSONLDContext
JSONLDContext

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization
GitHubOrganization

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity
DomainSecurity

Operate 1

Status, limits, changes, and where to get help

Support
Support

Company 2

The organization behind the API

LinkedIn
LinkedIn
 Website
Website

Other 1

Properties that don't map to a standard resource type

DataFormat
DataFormat

Source (apis.yml)

apis.yml Raw ↑ 
aid: unpaywall
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: medium
  source:
  - plans
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/unpaywall.png
name: Unpaywall
description: The Unpaywall REST API gives anyone free, programmatic access to the Unpaywall database of open access scholarly
  articles. The database covers over 120 million articles with Crossref DOIs and provides free, legal full-text links where
  available, with metadata on OA status (gold, hybrid, bronze, green), host type (publisher, repository), version (published,
  accepted, submitted), and license information.
url: https://raw.githubusercontent.com/api-evangelist/unpaywall/refs/heads/main/apis.yml
created: '2025-02-06'
modified: '2026-05-19'
specificationVersion: '0.19'
type: Index
tags:
- Open Access
- Scholarly Articles
- Research
- Academic
- Libraries
- DOI
- Science
apis:
- aid: unpaywall:unpaywall-doi-lookup-api
  name: Unpaywall DOI Lookup API
  description: Look up open access status by DOI
  humanURL: https://unpaywall.org/products/api
  baseURL: https://api.unpaywall.org/v2
  tags:
  - DOI Lookup
  properties:
  - type: OpenAPI
    url: openapi/unpaywall-doi-lookup-api-openapi.yml
  - type: Documentation
    url: https://unpaywall.org/products/api
  - type: SpectralRules
    url: https://raw.githubusercontent.com/api-evangelist/unpaywall/refs/heads/main/rules/unpaywall-rules.yml
  - type: JSONSchema
    url: https://raw.githubusercontent.com/api-evangelist/unpaywall/refs/heads/main/json-schema/unpaywall-article-schema.json
- aid: unpaywall:unpaywall-search-api
  name: Unpaywall Search API
  description: Search articles by title
  humanURL: https://unpaywall.org/products/api
  baseURL: https://api.unpaywall.org/v2
  tags:
  - Search
  properties:
  - type: OpenAPI
    url: openapi/unpaywall-search-api-openapi.yml
  - type: Documentation
    url: https://unpaywall.org/products/api
  - type: SpectralRules
    url: https://raw.githubusercontent.com/api-evangelist/unpaywall/refs/heads/main/rules/unpaywall-rules.yml
  - type: JSONSchema
    url: https://raw.githubusercontent.com/api-evangelist/unpaywall/refs/heads/main/json-schema/unpaywall-article-schema.json
common:
- type: AgenticAccess
  url: agentic-access/unpaywall-agentic-access.yml
- type: DomainSecurity
  url: security/unpaywall-domain-security.yml
- type: GitHubOrganization
  url: https://github.com/ourresearch
- type: LinkedIn
  url: https://www.linkedin.com/company/impactstory
- type: Website
  url: https://unpaywall.org
- type: Documentation
  url: https://unpaywall.org/products/api
- type: DataFormat
  url: https://unpaywall.org/data-format
- type: Support
  url: https://support.unpaywall.org
- type: Vocabulary
  url: https://raw.githubusercontent.com/api-evangelist/unpaywall/refs/heads/main/vocabulary/unpaywall-vocabulary.yml
- type: JSONLDContext
  url: https://raw.githubusercontent.com/api-evangelist/unpaywall/refs/heads/main/json-ld/unpaywall-context.jsonld
- type: LlmsText
  url: https://unpaywall.org/llms.txt
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com