Definition · Plain-language
Unpaywall
Unpaywall is a free database and browser extension that indexes and retrieves legal, open-access versions of peer-reviewed scholarly literature from institutional and publisher repositories.
The step most authors miss
Doing CRediT right? Don’t stop at the statement.
A CRediT statement credits you inside one paper. The recognition CRediT was built for happens when those roles are tied to you, persistently. Sign in with your ORCID — free — and claim your CRediT contributions on casrai.org, the home of the standard. They become a verified, portable part of your identity, not a line that disappears into one PDF.
Free: claim your contributions, then export a journal-ready CRediT statement, schema.org structured data, JATS XML, CSV or BibTeX — and preview your public profile. A membership publishes that profile publicly and verifies the journals you serve.
Data harvesting and legal open access
Unpaywall indexes legal open-access copies by harvesting metadata from over fifty thousand sources, including university repositories, government databases, and open-access publishers. The platform systematically avoids illegal document-sharing sites, focusing exclusively on files that authors have legally self-archived as green open access or that publishers have made freely available under gold open-access licences. This harvesting process uses the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) to query repositories continuously, ensuring users retrieve valid, copyright-compliant PDF documents. By maintaining a clean index of legal alternatives, the database helps researchers locate free versions of articles while respecting the intellectual property rights of academic publishers.
Browser extension and library integration
For individual academic users, the platform is best known as a browser extension compatible with major web browsers. When a researcher views a paywalled journal article, the extension checks the article's unique Digital Object Identifier (DOI) against the extensive Unpaywall database. If a legal open-access version is found, a prominent green padlock icon appears on the screen, linking the user directly to the PDF. This utility is also integrated into library catalogues and discovery layers globally, including systems like Primo and Summon, automating open-access discovery for students and faculty. This integration allows libraries to seamlessly bypass subscription barriers and direct patrons to legitimate free versions of paywalled literature.
API and metadata utility
Unpaywall offers a free, high-speed REST API used by reference managers, search engines, and academic databases to enrich their metadata. Tools like Scopus, Web of Science, and Zotero use this API to display open-access links to their users. Academic libraries also analyse their collections using the database, tracking how much of their faculty’s output is open-access and optimising journal subscription budgets. By integrating these metadata feeds, institutions can systematically evaluate the open-access status of published works, helping library administrators make evidence-based decisions about package subscriptions and open-access funding models. Furthermore, researchers utilise the complete data dump for bibliometric studies and policy analysis.
Key facts
At a glance
- Free, legal database of open-access scholarly articles operated by OurResearch
- Harvests metadata from university, institutional and publisher repositories
- Integrates with web browsers to show a green padlock for free PDFs
- Links exclusively to copyright-compliant green and gold open-access sources
- Provides a high-speed API used by major databases like Scopus and Web of Science
- Helps university libraries assess open-access rates and manage subscription budgets
Common misconceptions
What people often get wrong
Often heard: Unpaywall is a pirate site that illegally hosts copy-protected journal articles.
Actually: It is a fully legal tool that only indexes and links to files that have been officially made open-access by publishers or self-archived by authors.
Often heard: The Unpaywall extension will bypass security to unlock any paper on the internet.
Actually: It can only locate articles if a legal, open-access version has been deposited in an indexed repository. If no public version exists, it remains locked.
Common questions
FAQ
Is Unpaywall safe and legal to use?+
Yes, Unpaywall is legal and safe. It is operated by a non-profit organisation and only links to documents that are officially authorized for public access under copyright rules.
How does Unpaywall find open-access papers?+
It queries a massive index built by crawling open-access repository systems, library databases, and metadata feeds from publishers using the article’s Digital Object Identifier (DOI).
Going deeper
