There is no doubt that Sci-Hub, the infamous—and, according to a U.S. court, illegal—online repository of pirated research papers, is enormously popular. (See Science’s investigation last year of who is downloading papers from Sci-Hub.) But just how enormous is its repository? That is the question biodata scientist Daniel Himmelstein at the University of Pennsylvania and colleagues recently set out to answer, after an assist from Sci-Hub.
Their findings, published in a preprint on the PeerJ journal site on 20 July, indicate that Sci-Hub can instantly provide access to more than two-thirds of all scholarly articles, an amount that Himmelstein says is “even higher” than he anticipated. For research papers protected by a paywall, the study found Sci-Hub’s reach is greater still, with instant access to 85% of all papers published in subscription journals. For some major publishers, such as Elsevier, more than 97% of their catalog of journal articles is being stored on Sci-Hub’s servers—meaning they can be accessed there for free.