Unpaywall API Guide

Overview

Unpaywall is a free, open database of over 40 million free scholarly articles. Built by the nonprofit OurResearch, Unpaywall indexes legal open access (OA) copies of papers from thousands of institutional repositories, preprint servers, publisher websites, and government archives. It is the most comprehensive source for finding freely available versions of paywalled academic literature.

Researchers, librarians, and tool developers use Unpaywall to locate open access copies of papers they need, assess the OA status of publications, and integrate OA discovery into their workflows. The database is updated daily, scanning repositories and publisher sites for new open access content. Unpaywall categorizes OA into types: gold (published OA), green (repository copy), hybrid (OA in subscription journal), and bronze (free to read on publisher site).

The API requires only an email address for authentication and is free for non-commercial use with a generous rate limit of 100,000 requests per day.

Authentication

Authentication is via email address passed as a query parameter. No API key or registration is needed -- just provide a valid email:

?email=your@email.com

This email is used for contact purposes only and to identify your application. The API will reject requests without a valid email address. For commercial use or higher rate limits, contact OurResearch for an API key.