The peer review process for journal articles can be painfully slow. It can take months (or even years!) for an article manuscript to be reviewed and revised, sometimes requiring multiple submissions, reviews, revisions, and additional experiments or analysis. Meanwhile, the scientific or technical results contained in the manuscript as it undergoes review remain "undiscoverable" to practitioners.
A preprint is a manuscript prepared for publication as a journal article that gets shared prior to full peer review by a journal. Why do that? Publishing preprints enables the immediate sharing of unvetted research results so other researchers don't have to wait so long to discover research that has already been done.
Preprint sharing has several advantages:
Speeds up sharing of new findings and makes them freely accessible.
Helps researchers establish priority of work.
Demonstrates "work in progress" to employers and funders.
Opens up manuscripts to review and commentary from all readers.
Preprints may have disadvantages too:
Has not undergone peer review, so reader beware!
May be of lesser (or indeterminate) value compared to a "published" work.
This 2019 study found that preprint posting increased citations and media mentions. Read more from the non-profit group SPARC about the value of preprints during the COVID epidemic and review some arguments against preprints in an article published by Nature. In all cases, researchers should be aware of the pre-peer review status when reading and citing preprints, just as they should look out for errors missed in peer reviewed articles.
In March of 2022 Elsevier announced "preprints" as a new document type available on Engineering Village. Over 800,000 open access preprints from the arXiv database (from 2017 onwards) and the SSRN database are now findable within Compendex, with more coming in the near future.
