One definition of a preprint is a manuscript or article draft that has not been submitted or accepted for publication. A preprint server is defined as an online collection of preprints that are posted and made publicly available for viewing and comment. Preprints got their start in physics with arXiv which expanded to include other disciplines. With physics and mathematics leading the way, other disciplines gradually exchanged preprints and created preprint servers.
How do Preprint Servers Work? Scholars deposit their preprints in order to solicit feedback to their drafts so they can make improvements. More subject areas are starting to use these as another way to get ideas, solicit feedback, network, and collaborate with others.
Arguments For and Against Preprint Servers. Some scholars criticize preprint servers as providing ways for their work to be scooped. Some publishers may not accept manuscripts posted in these servers ("Inglefinger Rule") although this is decreasing; if interested in submitting your manuscript to a publisher, check their policy about this. Others argue that these servers have value in time-stamping an original idea to a scholar or their team, increasing the visibility of one's work, and with facilitating a larger or more rapid exchange of ideas. Consider your discipline norms and other variables that may apply to deciding whether or not to post your pre-published work in a preprint server.
The COVID pandemic also brought preprints and preprint servers in the spotlight. Many saw value in prints for exchanging new information that may lead to accelerating research to halt the pandemic. However, many poor quality studies in preprint servers were often cherrypicked to support a particular agenda. Preprints can also be confusing for those who are unfamiliar with scholarly publishing norms since a preprint may be different than a final version of record.
Manuscript Versions, from Draft to Version of Final Record (Graphic)
See this graphic for the progression of a manuscript to its final published format. Depending on which step it is in the publication process, authors have the ability to share or submit their preprint to a repository or preprint server.
Image Source: Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Preprint_postprint_published.svg. Permission by CC-BY 4.0
iBiology (2016). What are preprints? [YouTube video]. https://youtu.be/2zMgY8Dx9co