Historically, preprints have not been included in major indexes of biomedical literature. However, the COVID-19 pandemic, as well as the increasing acceptance of preprints by funding agencies as evidence of research output, have prompted some producers of journal indexes to include preprints in their databases. Preprints can now be found on Scopus, Web of Science, OpenAlex, Dimensions, and Lens.

In PubMed and PubMed Central, you can find preprints that report NIH-supported research on the SARS-CoV-2 virus and COVID-19, along with other topics. The first phase of this pilot project began in 2020. This phase included preprints with NIH support identified in the iSearch COVID-19 Portfolio tool developed by the NIH Office of Portfolio Analysis.

Phase 2 of the NIH Preprint Pilot launched on January 30, 2023, expanding beyond SARS-CoV-2 to all preprints with NIH support identified. Only preprints that have NIH-affiliated authors or acknowledge NIH support in the preprint are included. Learn more about the NIH Preprint Pilot Project.

Europe PMC, a member of the PubMed Central International Network, also includes a growing international preprint library from a variety of preprint servers. Learn more about Europe PMC.