AbstractThe world continues to face an ongoing viral pandemic that presents a serious threat to human health. The virus underlying the COVID-19 disease, SARS-CoV-2, has caused over 3.2 million confirmed cases and 220,000 deaths between January and April 2020. Although the last pandemic of respiratory disease of viral origin swept the globe only a decade ago, the way science operates and responds to current events has experienced a paradigm shift in the interim. The scientific community has responded rapidly to the COVID-19 pandemic, releasing over 16,000 COVID-19 related scientific articles within 4 months of the first confirmed case, of which at least 6,000 were hosted by preprint servers. We focused our analysis on bioRxiv and medRxiv, two growing preprint servers for biomedical research, investigating the attributes of COVID-19 preprints, their access and usage rates, characteristics of their sharing on online platforms, and the relationship between preprints and their published articles. Our data provides evidence for increased scientific and public engagement (COVID-19 preprints are accessed and distributed at least 15 times more than non-COVID-19 preprints) and changes in journalistic practice with reference to preprints. We also find evidence for changes in preprinting and publishing behaviour: COVID-19 preprints are shorter, with fewer panels and tables, and reviewed faster. Our results highlight the unprecedented role of preprints and preprint servers in the dissemination of COVID-19 science, and the likely long-term impact of the pandemic on the scientific publishing landscape.