What is the difference between a preprint and a peer-reviewed paper?
Updated: 2026-09-09 · Safety and evidence
Short answer
A preprint is a manuscript the authors post before external review. It shares results quickly, but nobody outside the team has yet checked the methods or the analysis. A peer-reviewed paper has passed that filter, which does not guarantee it is correct — only that it was examined.
In plain English
- Preprints live on repositories such as bioRxiv or medRxiv and carry an explicit notice.
- Many preprints are eventually published with substantial changes to data or conclusions.
- Some are never published, sometimes because review found problems.
- When reading news coverage, check whether the source is a preprint or a final paper.
What we know
- Preprint repositories require a statement that the work has not been peer reviewed.
- Preprint use accelerated across biomedicine in recent years.
What we don't know yet
- You cannot tell in advance which preprints will survive review unchanged.
- Quality varies widely between preprints: the label says nothing about a specific paper's rigour.
Sources
External links to official sources or peer-reviewed studies.