Open Access

Daniel S. Himmelstein, Ariel Rodriguez Romero, Stephen Reid McLaughlin, Bastian Greshake Tzovaras, Casey S. Greene​

• The website Sci-Hub provides access to scholarly literature via full text PDF downloads. The site enables users to access articles that would otherwise be paywalled. Since its creation in 2011, SciHub has grown rapidly in popularity. However, until now, the extent of Sci-Hub’s coverage was unclear. As of March 2017, we find that Sci-Hub’s database contains 68.9% of all 81.6 million scholarly articles, which rises to 85.2% for those published in toll access journals. Coverage varies by discipline, with 92.8% coverage of articles in chemistry journals compared to 76.3% for computer science. Coverage also varies by publisher, with the coverage of the largest publisher, Elsevier, at 97.3%. Our interactive browser at greenelab.github.io/scihub allows users to explore these findings in more detail. We find Sci-Hub preferentially covers popular, paywalled content, containing 96.2% of citations to toll access journals since 2015. For recently requested articles by Unpaywall users, oaDOI provided access to 48.8% whereas Sci-Hub contained 81.5%. Together, oaDOI and Sci-Hub covered 94.1%, demonstrating that gaps in Sci-Hub’s coverage, especially for open access articles, can be filled using licit services. For the first time, nearly all scholarly literature is available gratis to anyone with an Internet connection. Sci-Hub’s scope suggests the subscription publishing model is becoming unsustainable.