Models of OA: Green and Gold

Most paths to open access can be grouped into two major categories: self-archiving ("green" open access), or open access publishing ("gold" open access). Gold open access encompasses many business models which are sometimes treated as distinct, including APC-funded open access and APC-free "diamond" or "platinum" open access.

*Diagram by Foster Open Science (PASTEUR4OA) illustrating the green and gold roads to Open Access. 

SElf-ARchiving (Green OA)

Green Open Access is achieved when authors openly share their work, for instance, on their website or in an institutional or disciplinary repository. Published works should be shared in accordance with publisher policies (the "green" in "green open access" is a reference to the publisher giving authors a green light to share their work). Green open access has two major benefits: it can be achieved in a wider variety of publishing venues, and it almost never involves paying fees.

Almost all scholarly publishers allow authors to share some version of their work. However, they often impose conditions, most frequently:

  • Restrictions on what version of the work can be shared.
  • Restrictions on when the work can be shared.

That is, publishers may not allow authors to share the formatted PDF of their work, but might still allow them to share the accepted manuscript, also known as the post-print, or the submitted manuscript, also known as the pre-print. Accepted manuscripts are very close to the published version of the work and have already undergone peer review, but don't have the publisher's fancy formatting.  Submitted manuscripts are not yet peer-reviewed, but they do help authors to get their work out faster.

Additionally, publishers will often impose embargoes, which delay sharing. These embargoes vary widely by discipline but most often range from six months to two years.

Publisher policies can be confusing, but there are resources to help navigate them.

  • Sherpa/Romeo is a directory of journal policies which lists the conditions under which each version of an article can be shared.
  • Share Your Paper is an open source tool that assists in identifying the policies for your article and will help you to upload it.

If you're unsure about publisher policies, you can check their website, or ask your friendly Scholarly Communication librarian.

If you are looking for a repository where you can share your work, there are some directories of repositories available:

You might also want to check where others in your field are sharing their work. Finally, academic social networks such as and ResearchGate are popular, but are not recommended because their business model appears to involve selling user data, and because they've famously received take-down notices from publishers. Indeed, some publishers specifically exclude them from their sharing policies.

Open Access Publishing (Gold OA)

Gold Open Access is achieved when works are made openly available directly via the publisher.  Gold open access has some major benefits: it's usually immediate, and open articles and chapters are easy to find on the publisher's website. Additionally, publishers often allow works published under gold open access to be given a Creative Commons license, which allows reuse. (Thus, works published in gold open access can also be made available via green open access!)

It is common, though not universal, for publishers to charge author fees for gold open access. These fees are referred to as APCs (article processing charges) or BPCs (book processing charges). Fully open access journals make all their articles open access. Some journals utilize a "hybrid" model wherein articles are only made open access if the author pays a fee, while the journal continues to operate under a subscription model. Publishers may refer to this euphemistically as "author choice" or "open choice."

Author fees are often covered by authors' funders, institutions, or libraries. Authors who know they want to publish in APC-supported journals should consider including these funds in their grant proposals. It is also becoming more common for fees to be covered under what's called a "transformative agreement" or a "read and publish agreement," which bundles author fees in with the library's subscription costs for a publisher.

Open access publishing models that do not involve author fees are often referred to as "diamond" or "platinum" open access.

APC-free publications might be published under several different business models; for instance, they may be subsidized by a society or institution.  Recently, some publishers have also been developing the "subscribe to open" model, under which libraries can subscribe to their backlists, and if enough libraries subscribe, future publications are made openly available.

Finding Gold (OA) publishers: Two tools are especially useful:

  • DOAJ​​​​ (Directory of Open Access Journals) for open access journals

    • When searching in DOAJ, you can use a filter to search for journals "without article processing charges (APCs)"

  • DOAB (Directory of Open Access Books) for open access books.