Unpaywall
The one-click route to a legal free version of almost any paper.
At a Glance
- Publisher
- OurResearch (US nonprofit)
- Coverage
An open database of 30M+ free-to-read scholarly articles harvested from repositories and OA journals, keyed by DOI (verify current counts).
- Access
Free; browser extension, open API, and data snapshot.
- Free alternative
- It is free; Google Scholar for a broader (messier) search.
- Regional
Global, following the open literature.
Our Take
Unpaywall does one thing brilliantly: given a DOI or a paywalled page, it finds the legal open-access version if one exists, drawing only on author-posted and publisher OA copies (never pirated ones). The browser extension is a daily-driver for researchers, and the API and snapshot power much of the open-access ecosystem, including many library link-resolvers. It’s not a discovery tool — you bring the paper, it finds the free copy. Use it constantly to get full text legally; build on the API when you need OA-status data at scale.
Power Tips
- Install the browser extension so a green tab appears whenever a free version exists.
- Use the API to add open-access status and links to your own datasets at scale.
- Remember it only surfaces legal OA copies — absence means no free version, not a broken link.
Alternatives & Complements
Open Access Button, CORE, Google Scholar, Semantic Scholar
Figures last verified: June 15, 2026