Preprint

A preprint is a version of a research paper that is shared publicly before undergoing formal peer review and journal publication. Preprints are typically hosted on dedicated servers such as arXiv (physics, mathematics, computer science and related fields), bioRxiv (biology), medRxiv (medical sciences), and SSRN (social sciences). They receive a digital object identifier (DOI) upon posting and become permanently part of the scholarly record, even if the paper is later revised or published in a journal.

Preprints accelerate the pace of scientific communication, reducing the time between completing a study and sharing its findings from months or years to days. This speed is critical during public health emergencies, as demonstrated during the COVID 19 pandemic, when preprints became a primary channel for disseminating urgent research findings. Preprints also allow researchers to establish priority for their discoveries, receive early feedback from the broader community before formal submission, and make their work freely accessible regardless of journal paywalls. However, the absence of peer review means that preprint findings must be interpreted with caution, as they have not been evaluated by independent experts for methodological rigor, statistical accuracy, or interpretive validity.

To post a preprint, researchers submit their manuscript to a preprint server. Most servers perform basic screening for ethical compliance, scope relevance, and formatting but do not conduct substantive peer review of the scientific content. The manuscript is typically posted within a few days and assigned a DOI, making it permanently citable. Authors can update their preprint with revised versions as they receive feedback or in response to peer review comments from a journal submission.

Most major journals, including those published by Elsevier, Springer Nature, and Wiley, now accept submissions of papers that have been posted as preprints, a reversal from earlier policies that treated preprint posting as prior publication. Some journals have integrated preprint posting into their submission workflow, automatically posting manuscripts on a linked server at the time of submission.

The relationship between preprints and the peer reviewed literature is evolving. Studies have found that most preprints in the life sciences are eventually published in peer reviewed journals: in one analysis, about two thirds of bioRxiv preprints posted in 2016 or earlier had been published, and comparisons of preprints with their published versions usually find changes that do not alter the main conclusions. Some preprints are corrected or withdrawn before formal publication when early community feedback identifies errors. In systematic reviews, the inclusion of preprints is debated: excluding them may miss relevant evidence, while including them introduces studies that have not undergone quality review. When preprints are included, reviewers should note their status and consider the findings as preliminary.

Post a preprint when rapid dissemination is important, when you want early community feedback, or when you wish to establish priority for your findings. Preprints are particularly valuable during public health emergencies, in fast moving fields, or when journal review timelines are long. Do not treat preprint findings as equivalent to peer reviewed evidence when making clinical or policy decisions. When including preprints in a literature review or systematic review, clearly label them as non peer reviewed and consider conducting a sensitivity analysis with and without preprints to assess their influence on the conclusions.

A major error is citing preprints in clinical guidelines or media reports without clearly disclosing their non peer reviewed status, which can lead to premature adoption of unvalidated findings. Another mistake is assuming that preprints are inherently lower quality; many preprints present rigorous work that will pass peer review with minor revisions. Researchers sometimes post preprints and then neglect to update them after peer review, leaving outdated versions as the most visible record. Finally, some researchers are unaware that certain journals still have restrictive preprint policies, and posting a preprint could jeopardize submission to those outlets.

During an emerging infectious disease outbreak, a virology laboratory completes a study characterizing the immune response to a novel pathogen in 120 healthcare workers. Rather than waiting six to twelve months for journal publication, they post the manuscript on medRxiv. Within one week, immunologists from three countries provide feedback identifying a potential confound in the serological assay. The authors repeat the analysis with an improved protocol, post a revised preprint, and submit the corrected version to a peer reviewed journal, where it is published four months later.