Preprints Without Curation Are Increasingly Cited by Journals

The recent strain on peer review systems necessitates the publish-review-curate model, where the public dissemination of manuscripts is decoupled from formal peer review and later editorial processes. Citation norms traditionally pointed to the curated version; those that subsequently appear in peer-reviewed journals. Citations to preprints are therefore generally expected to occur only to those eventually curated. Using metadata from six major preprint servers linked to the world's largest bibliographic reference database, and focusing on citations from long-established journals with rigorous editorial workflows, we compare observed citation rates with a null model reflecting the expected rate if authors were indifferent between preprints and journal articles. The growth is evident in both citation intensity and the breadth of adoption: at its peak in 2021, nearly one in five journal articles cited at least one preprint. The preference to cite preprints has grown exponentially since the mid-2010s, with key inflection points coinciding with the launch of bioRxiv (2013) and the introduction of a preprint content type in Crossref's DOI system (2016). An increasing share of these citations refer to non-curated preprints and this shift cannot be explained by confounding factors: the growing stock of preprints, faster publishing cycles, or the outsized influence of a small set of highly cited preprints. These findings reveal a structural shift in citing behavior: preprints are increasingly treated as legitimate, autonomous objects of citation, independent of their later publication status, motivating renewed attention to how citation conventions and journal policies should accommodate the expanding role of preprints in scholarly communication. The COVID-19 pandemic did not amplify this trend but instead coincided with a deceleration in preprint citation growth.