What is a preprint? arXiv, bioRxiv and medRxiv explained

A preprint is a complete research paper that the authors post online before it has been peer reviewed by a journal. Anyone can read it for free, usually within a day or two of posting.

How preprints work

1. The authors write their paper as usual.
2. They upload it to a preprint server, which does a quick basic check (is it real research, is it in scope?) but not full peer review.
3. The preprint gets a permanent link and often a DOI, so others can read and cite it.
4. Most authors also submit the paper to a journal. When it is published, the preprint is usually linked to the final version.

The main preprint servers

Many countries and fields have their own servers too, and some journals now publish open peer-review reports alongside preprints.

Why researchers post preprints

• Speed: results are public in days instead of the months a journal can take.
• Priority: the posting date shows who found something first.
• Feedback: other researchers can comment before the final version.
• Free access: anyone, anywhere, can read the work.

Preprints became widely known during the COVID-19 pandemic, when fast sharing of results mattered most.

How to read a preprint carefully

Because preprints have not been peer reviewed:

• Treat the results as preliminary — they may change or be corrected later.
• Check whether a published version exists (the preprint page usually links to it).
• Look at the methods and sample size before trusting big claims.
• Be careful when sharing preprint findings on social media or in news stories; say clearly that the work is not yet peer reviewed.

Preprints in ResearchBoard

ResearchBoard counts preprints together with journal articles, reviews, letters, conference papers and book chapters. See how many papers are published every day and how to find research papers for free.