Green Open Access publishing (referred to as Green OA) is a type of publishing sometimes referred to as self-archiving, where the user deposits their manuscript into a repository of their choice. Sometimes, the user can deposit a preprint, which is a version of their manuscript that precedes formal peer review, into a preprint server like bioRxiv.org or medRxiv.org. It is highly recommended that the preprint is protected by a Creative Commons License before it is deposited into a preprint server.
Preprint deposits popularity rose at the height of the COVID-19 pandemic, when getting information out quickly was critical, and continues to be a great option. Since preprints skip the peer review process, ideas and concepts are shared more quickly and more broadly. Another option, also called a postprint or an Author Accepted Manuscript (AAM), is the version of the manuscript after it has been completely peer reviewed that can be deposited into a repository. PubMed Central (PMC) is a popular federal repository that often receives postprints like these in their archive. In theory then, you can publish free, non-OA and get your AAM into a digital repository like PMC to get your research out there for the world to freely access.
Diamond Open Access publishing (referred to as Diamond OA) does not charge APCs to make your publication free for the public and world to read and publish. So how do Diamond Open Access publishers sustain themselves? These publishers are typically academic-led and community-driven, leveraging support from institutional, governmental, and volunteer sources to cover their operational costs. Universities and libraries are often major funders, absorbing the costs of publishing as part of their commitment to scholarship and open science.
Here at Hopkins, the JH Libraries support a preprint peer review service and Diamond Open Access journal known as Peer Community In (PCI). A preprint that has been peer reviewed by PCI can be accelerated for publication through skipping the peer review process for PCI-friendly journals and at PCI’s Diamond Open Access Journal, Peer Community Journal.
Learn more about the world of preprints, Green and Diamond Open Access publishing, and PCI, at the PCI Keynote Talk on Friday, October 24, 2025 from 11:00 AM to 12 noon EDT. Registration is required.