After many months of planning, we are launching the Preprint Citation Index, a multidisciplinary collection of preprints from leading repositories that helps researchers stay current with the newest research while maintaining confidence in the resources they rely on. . . . The Preprint Citation Index currently provides nearly two million preprints from arXiv, bioRxiv, chemRxiv, medRxiv and Preprints.org. We plan to add preprints from a dozen additional repositories as well as display open peer reviews on Preprint Citation Index throughout 2023.