Unpaywall Has a Free API — Find Open Access Versions of Any Paywalled Paper

You find the perfect paper for your research. You click the link. And you hit a $40 paywall. But what if that same paper is legally available for free somewhere else? Unpaywall checks 50,000+ open-access sources to find free legal copies of paywalled papers. It covers 30M+ articles. And it has a free API. How It Works Give Unpaywall a DOI, and it tells you: Is there a free legal version? Where is it hosted? (university repo, preprint server, author page) What type of open access? (gold, green, hybrid, bronze) Quick Start import requests def find_free_version(doi, email): resp = requests.get(f"https://api.unpaywall.org/v2/{doi}", params={"email": email}) data = resp.json() if data.get("is_oa"): best = data.get("best_oa_location", {}) print(f"FREE version found!") print(f" URL: {best.get('url_for_pdf') or best.get('url')}") print(f" Host: {best.get('host_type')} ({best.get('repository_institution', 'N/A')})") print(f" OA type: {data.get('oa_status')}") else: print(f"No free version found