Unpaywall is an online service that finds and collects open access literature scattered across the internet, producing an online database of almost 24 million free scholarly articles. Unpaywall finds this content by harvesting online databases, open access repositories, and journal sites for legally-uploaded content that (1) has a Crossref-assigned Digital Object identifier (DOI); and (2) is available to anyone without registration or payment.
Unpaywall works behind the scenes in thousands of library systems, search platforms, and other information products worldwide.
Particular digital systems using Unpaywall that may be familiar to the Caltech community include:
