Content Access

Open access tools for academic papers

Unpaywall browser extension

Unpaywall finds free, legal copies of 20+ million academic papers.

# Unpaywall API (free, requires email for identification)
import requests

def find_open_access(doi: str, email: str) -> dict:
    """Find open access version of a paper using Unpaywall API.

    Args:
        doi: Digital Object Identifier (e.g., "10.1038/nature12373")
        email: Your email for API identification

    Returns:
        Dict with best open access URL if available
    """
    url = f"https://api.unpaywall.org/v2/{doi}?email={email}"

    response = requests.get(url, timeout=30)

    if response.status_code != 200:
        return {'error': f'Status {response.status_code}'}

    data = response.json()

    if data.get('is_oa'):
        best_location = data.get('best_oa_location', {})
        return {
            'is_open_access': True,
            'oa_url': best_location.get('url_for_pdf') or best_location.get('url'),
            'oa_status': data.get('oa_status'),  # gold, green, bronze, hybrid
            'host_type': best_location.get('host_type'),  # publisher, repository
            'version': best_location.get('version')  # publishedVersion, acceptedVersion
        }

    return {
        'is_open_access': False,
        'title': data.get('title'),
        'journal': data.get('journal_name')
    }

# Usage
result = find_open_access("10.1038/nature12373", "[email protected]")
if result.get('is_open_access'):
    print(f"Free PDF at: {result['oa_url']}")

CORE API (295M papers)

# CORE API - requires free API key from https://core.ac.uk/

import requests

class CORESearch:
    def __init__(self, api_key: str):
        self.api_key = api_key
        self.base_url = "https://api.core.ac.uk/v3"

    def search(self, query: str, limit: int = 10) -> list:
        """Search CORE database for open access papers."""

        headers = {'Authorization': f'Bearer {self.api_key}'}
        params = {
            'q': query,
            'limit': limit
        }

        response = requests.get(
            f"{self.base_url}/search/works",
            headers=headers,
            params=params,
            timeout=30
        )

        if response.status_code != 200:
            return []

        data = response.json()
        results = []

        for item in data.get('results', []):
            results.append({
                'title': item.get('title'),
                'authors': [a.get('name') for a in item.get('authors', [])],
                'year': item.get('yearPublished'),
                'doi': item.get('doi'),
                'download_url': item.get('downloadUrl'),
                'abstract': item.get('abstract', '')[:500]
            })

        return results

    def get_by_doi(self, doi: str) -> dict:
        """Get paper by DOI."""
        headers = {'Authorization': f'Bearer {self.api_key}'}

        response = requests.get(
            f"{self.base_url}/works/{doi}",
            headers=headers,
            timeout=30
        )

        return response.json() if response.status_code == 200 else {}

Semantic Scholar API (214M papers)

# Semantic Scholar API - free, no key required for basic use

import requests

def search_semantic_scholar(query: str, limit: int = 10) -> list:
    """Search Semantic Scholar for papers with open access links."""

    url = "https://api.semanticscholar.org/graph/v1/paper/search"
    params = {
        'query': query,
        'limit': limit,
        'fields': 'title,authors,year,abstract,openAccessPdf,citationCount'
    }

    response = requests.get(url, params=params, timeout=30)

    if response.status_code != 200:
        return []

    results = []
    for paper in response.json().get('data', []):
        oa_pdf = paper.get('openAccessPdf', {})
        results.append({
            'title': paper.get('title'),
            'authors': [a.get('name') for a in paper.get('authors', [])],
            'year': paper.get('year'),
            'citations': paper.get('citationCount', 0),
            'open_access_url': oa_pdf.get('url') if oa_pdf else None,
            'abstract': paper.get('abstract', '')[:500] if paper.get('abstract') else ''
        })

    return results

def get_paper_by_doi(doi: str) -> dict:
    """Get paper details by DOI."""
    url = f"https://api.semanticscholar.org/graph/v1/paper/DOI:{doi}"
    params = {
        'fields': 'title,authors,year,abstract,openAccessPdf,references,citations'
    }

    response = requests.get(url, params=params, timeout=30)
    return response.json() if response.status_code == 200 else {}

Browser reader mode for soft paywalls

Activating reader mode

// Bookmarklet to trigger Firefox-style reader mode
// Works on some soft paywalls that load content before blocking