Reading science
What is a preprint and how to read one with care
A preprint is a complete draft shared before a journal certifies it through peer review. You can read it, but it helps to know which stage it is at.
A quick way to choose
- A preprint is a public draft of a scientific work that has not yet been certified by peer review.
- Repositories display notices that say so, and they run basic screening before posting. That is not the same as endorsing the results.
- Before citing one, check whether a journal version exists and what changed between the two.
You came across a news story that cites a study, and when you open the link the page says it is a preprint. That word does not mean the work is bad or reliable. It tells you where the work is on its path. This guide helps you place it and decide how to use it.
If all you have is the headline, first find the original work with this guide to finding the study behind a news story.
What a preprint is
The US National Library of Medicine (NLM) defines preprints as complete and public drafts of scientific documents, not yet certified by peer review. The same source says that certification is the key distinction from an accepted author manuscript or a published article.
In peer review, a journal’s editors ask specialists to assess the work, and those experts may identify weaknesses in its assumptions, methods and conclusions. With a preprint, that step has not happened yet or is still under way. Not having it yet does not make a paper false. It means one control stage is still missing, and you should keep that in mind while reading.
Where they are posted and what gets checked
bioRxiv, for the life sciences, and medRxiv, for the health sciences, are two of these repositories. bioRxiv states that its articles are not peer-reviewed, edited or typeset before being posted. All of them go through a basic screening for offensive or non-scientific content, for material that might pose a health risk, and for plagiarism. It also notes that appearing on the site does not imply an endorsement of a paper’s methods, conclusions or scientific quality. About bioRxiv.
medRxiv explains that authors are solely responsible for the content and that a preprint may contain errors or omissions. It asks journalists and others who report on medical research to keep in mind that the work has yet to be evaluated by the medical community. medRxiv FAQ.
How to tell you are looking at one
Look for the notice first. On medRxiv, every preprint carries a prominent statement that it has not been certified by peer review and should not be used to directly inform clinical decision-making, and PDFs carry a stamp with that warning.
If you found it in PubMed or PubMed Central, look for the information panel saying the article has not yet been peer reviewed and for the Preprint label on the record. NLM explains that these records link to the full text on the repository’s own website. NIH Preprint Pilot.
Check whether a journal has published it
Many preprints are submitted to journals, and NLM cautions that any aspect of the research, including the results and conclusions, may change as a result of peer review. That is why it helps to know whether a published version exists.
On the preprint’s page, look for a link to the published version. medRxiv says it usually adds that link automatically about two weeks after journal publication, and that on rare occasions a match is not made for technical reasons. If you see no link, search for the exact title in PubMed or on the journal’s website. If you find both versions, compare them before settling on a conclusion.
Preprints can also be revised. Note the version number and the date of the one you read. If the work has been published, also check whether the journal added corrections or retractions with this guide to checking if a paper was retracted or corrected.
How to read one with care
You can read a preprint like any other paper: start with the question, move on to the methods and look at which data back each claim. Our guide to reading a research paper offers a step-by-step route. With a preprint, add these questions:
- What does it say about its own status? Look for the notice and for a published version.
- Which version did I read, and what is its date?
- What does the text claim based on its own data, and what does the news story that cites it add?
- Are the conclusions written as firm results or as preliminary findings?
- If the topic is health, am I using the text to learn or to make a decision? For decisions about treatment, talk to a health professional.
Leave a note that says how much you know
When you save a preprint, write its status next to it. For example: Preprint on medRxiv, version 2, checked on November 6, 2026, no published version found. If you cite or share it later, that line keeps you from presenting it as a result that has already been reviewed.
If you want to practise with a short read, you can explore the PaperFlow readings and check each source for the stage of publication it is at.
How we prepared this guide
PaperFlow publishes this guide, prepared with AI assistance and editorial review of the official definitions from the US National Library of Medicine, medRxiv and bioRxiv on November 6, 2026. Descriptions of notices and links reflect those pages on that date, and each repository may change them. We do not assess the quality of any particular preprint.