AbstractResearchers in the life sciences are posting work to preprint servers at an unprecedented and increasing rate, sharing papers online before (or instead of) publication in peer-reviewed journals. Though the increasing acceptance of preprints is driving policy changes for journals and funders, there is little information about their usage. Here, we collected and analyzed data on all 37,648 preprints uploaded to bioRxiv.org, the largest biology-focused preprint server, in its first five years. We find preprints are being downloaded more than ever before (1.1 million tallied in October 2018 alone) and that the rate of preprints being posted has increased to a recent high of 2,100 per month. We also find that two-thirds of preprints posted before 2017 were later published in peer-reviewed journals, and find a relationship between journal impact factor and preprint downloads. Lastly, we developed Rxivist.org, a web application providing multiple ways of interacting with preprint metadata.