Sci-Hub collected a database of 88,343,822 research documents, freely available for download. Around 80% of the collection are research articles published in journals, 6% are papers from conference proceedings, 5% are book chapters, the rest are other types of documents.

Sci-Hub has amassed an extensive database of research documents, which currently stands at 88,343,822 items.13 The primary focus of this collection is on research articles that have been published in various scientific journals, accounting for approximately 80% of the total documents available.1 In addition to journal articles, the database also includes other forms of scholarly communication, such as papers from conference proceedings, which make up about 6% of the collection,1 and book chapters, which constitute 5% of the documents.1 The remaining portion of the database is comprised of various other types of research documents.1

The mission of Sci-Hub is to democratize access to scientific knowledge by providing free and unrestricted access to its entire collection.23 This is particularly significant given that a substantial portion of the scientific literature is published behind paywalls, making it inaccessible to those without institutional access or the means to pay for individual articles.4

Moreover, Sci-Hub's database is not only large but also comprehensive, with studies from March 2017 indicating that it contains a significant percentage of all scholarly articles. Specifically, it was found to include 68.9% of the 81.6 million scholarly articles indexed by Crossref, with this percentage increasing to 85.2% for articles published in toll-access journals.67 This suggests that Sci-Hub is a valuable resource for researchers and the general public seeking access to a wide range of scientific literature.

In summary, Sci-Hub's database is a vast and diverse collection of research documents, with a strong emphasis on journal articles, and it plays a crucial role in facilitating open access to scientific knowledge.89