Types of open access

Gold open access (OA) is a publishing model where the final, peer-reviewed version of an article is made freely available to everyone immediately upon publication. By removing paywalls, it ensures that researchers, practitioners, policymakers, and the general public can access scholarly work without the need for a subscription.

The initial publication of academic works as articles in open access journals, open access monographs, or as contributions to open access edited volumes or conference proceedings is referred to as open access publishing. Similar to closed access works, these texts typically go through the same quality assurance procedure, which primarily takes the form of editorial or peer review. Frequently, an open access publication license (e.g., Creative Commons) is included, allowing authors to define how their work can be reused and shared.

Both open access and closed access publications have to be funded. Funding options for open access publications are similar to those for closed access publications: advertising or sponsorship; sales of printed copies; and unpaid assistance from volunteers, scientific institutions, and the scientific community. Cross-financing also happens occasionally. Specifically, commercial publishers who wish to experiment with the open access business model use their subscription revenue to fund new journals.

Publication fees, also known as article processing charges (APCs; book processing charges, or BPCs for monographs), are common in closed access publishing even though they are occasionally mentioned as an example of a typical gold open access financing model. APCs can be combined with institutional memberships and are paid for each accepted and published article. The publication fees will be fully or partially covered by the publishing authors’ institution if that institution is an institutional member of an open access publisher. Furthermore, numerous institutions offer additional options for reimbursement of these expenses, such as through publication funds.

Key features of gold open access:

• immediate and permanent access: articles are freely accessible as soon as they are published, with no embargo periods. The final, formatted version (Version of Record) is openly available, complete with DOI assignment;
• published in open access journals: gold OA articles appear in fully open access journals (e.g., PLOS ONE, Nature Communications, and BMJ Open) or in hybrid journals where authors pay for OA at the article level;
• article processing charges (APCs): instead of charging readers, gold OA journals charge authors or their institutions a publishing fee - APC. APCs vary by journal, ranging from a few hundred to several thousand euros. Some journals offer waivers or discounts for authors from low-income countries or for early-career researchers;
• copyright and licensing: authors typically retain copyright and publish under a Creative Commons (CC) license, which specifies how others can reuse the article: CC BY (Attribution) – allows unrestricted reuse with proper credit; CC BY-NC (Non-Commercial) – free for non-commercial use; CC BY-SA (Share-Alike) – requires derivative works to have the same license. The author retains copyright instead of transferring it to the publisher.
• indexing and discoverability: gold OA journals are indexed in major databases like Scopus, Web of Science, and DOAJ (Directory of Open Access Journals), increasing article visibility and citation potential.

Types of gold open access journals:

• fully open access journals: all articles are openly available (e.g., PLOS ONE, eLife, Scientific Reports);
• hybrid open access journals: traditional subscription-based journals that allow authors to make individual articles open access by paying an APC. The rest of the journal content remains behind a paywall (e.g., Elsevier, Springer, Wiley hybrid journals).

Advantages of gold open access:

• maximized visibility & impact: more readers, higher citations;
• immediate access: no waiting for embargo periods;
• copyright retention: authors keep rights to their work;
• credibility & recognition: peer-reviewed and indexed in reputable databases.

Disadvantages of gold open access:

• high APCs: costly for some researchers, especially those without funding;
• quality concerns: some predatory publishers exploit the APC model without proper peer review;
• institutional limitations: not all universities or funders cover APCs.

Green open access (OA), sometimes referred to as self-archiving, allows authors to deposit a version of their work in an institutional or disciplinary open access repository while publishing in a traditional journal. It can also mean posting such a work on the author’s personal website, according to some interpretations. For preprints and post-prints of scholarly articles, as well as for other document types like monographs, research reports, and conference proceedings, self-archiving may occur concurrently with the publisher’s publication of the content or at a later time. Sometimes this allows readers to access the work for free, even if the final published version is behind a paywall.

Preprint and post-print

A preprint is a manuscript that has not undergone peer review, indicating that the work’s quality has not yet been determined with certainty. Preprints allow early dissemination of research but have not been formally validated.

A post-print, as opposed to a preprint, is a version that has passed peer review but has not been typeset by the publisher. Post-prints come in two varieties. On the one hand, a post-print might be exactly the same as the version of record or the publisher’s version. However, the formatting, layout, or pagination may differ even though the content is the same. The post-print in the latter instance is known as the author’s accepted manuscript (AAM) version. There is a wide range in publishers’ willingness to permit post-prints or preprints to be self-archived. An overview of the rights that publishers grant their authors in this area can be found in the Open Policy Finder database.

A version of record (VoR) is a final, publisher-formatted version, which is typically behind a paywall. Most Green OA policies allow self-archiving of postprints but not the VoR.

Variants of green open access

There are three distinct approaches to granting green open access in open access discussions. The first option is to make the works accessible through institutional repositories. In this instance, authors can choose to store their scientific writings on a transdisciplinary document server run by their university or other organization. Second, regardless of the institutions the authors are affiliated with, the works may be made available in disciplinary repositories, which are repositories that house output from a specific subject area (for example, a specialized discipline). Depositing academic papers on one’s own website is a third option. The deposited documents are typically less accessible with this method than they would be if they were kept in an institutional or disciplinary repository.

Key features of green open access:

• self-archiving in repositories: authors deposit a preprint (before peer review) or postprint (after peer review, but unformatted) in an open-access repository (institutional, subject-specific or general repositories);
• embargo periods: some publishers delay self-archiving for 6–24 months after publication. The length of the embargo depends on the publisher’s open access policy. During the embargo, only metadata (title, abstract, and citation details) may be freely available;
• no author fees (APCs): unlike gold OA, green OA is free for authors. The publishing process is still handled by traditional subscription-based journals;
• copyright and licensing: publishers may require authors to sign a copyright transfer agreement, limiting self-archiving rights. Some publishers allow self-archiving under Creative Commons (CC) licenses.

How to Publish via Green Open Access?

• check the journal’s OA policy: use tools like Open Policy Finder to find self-archiving policies for specific journals;
• choose the right version for deposit: if preprints are allowed, deposit the initial version of manuscript. If postprints are allowed, deposit the peer-reviewed manuscript (AAM);
• select a suitable repository: institutional repository (university-based), discipline-specific repository (e.g., arXiv, bioRxiv), general repository (e.g., Zenodo, SSRN);
• comply with embargo requirements: if an embargo applies, upload the file but set it to “restricted” until the embargo period ends.

Advantages of green open access:

• free for authors & readers: no APCs, increasing accessibility;
• increases visibility: broader academic reach;
• works alongside traditional publishing: authors can publish in prestigious journals and still provide free access.

Disadvantages of green open access:

• embargo delays: research may not be immediately accessible;
• different article versions: readers may access preprint instead of the final version, leading to inconsistencies;
• copyright restrictions: some publishers don’t allow self-archiving or limit it severely.

Diamond (sometimes called platinium) open access (OA) is a publishing model where academic research is freely available to both readers and authors, with no publication fees. It combines the immediacy of Gold OA with the cost-free model of Green OA, making it the most equitable form of open-access publishing.

The foundation of diamond open access publishing is frequently non-commercial and community-driven. Diamond open access journals typically rely on volunteer labor and fund their publications through institutional funding, crowdfunding, consortial models, or membership models.

Key features of diamond open access:

• free for both authors and readers: no subscription fees for readers and no article processing charges (APCs) for authors;
• immediate and permanent access: articles are immediately available to the public upon publication – no embargo period. Content remains permanently open, enhancing global access to knowledge;
• published in non-profit or community-supported journals: these journals are often funded by academic institutions, government agencies, libraries, or scientific societies. Many are community-driven and focus on specific research fields (e.g., Journal of Machine Learning Research, Epijournal de Géométrie Algébrique);
• copyright and licensing: articles are usually published under Creative Commons (CC) licenses (e.g., CC BY), allowing reuse with proper attribution. Authors retain copyright rather than transferring it to the publisher.

How diamond open access journals are funded?

Since neither authors nor readers pay fees, diamond OA relies on alternative funding models:

• institutional support: universities or research institutes cover publication costs;
• government grants: public funding supports journal operations and infrastructure;
• non-profit organizations: scholarly societies and independent foundations fund journals;
• voluntary contributions: some diamond OA journals rely on voluntary labor from academics (e.g., peer reviewers and editors).

Examples of diamond open access journals and platforms:

• SciPost: covers physics and mathematics research;
• Open Library of Humanities (OLH): supports humanities and social sciences journals;
• Episciences: hosts peer-reviewed overlay journals in mathematics and computer science;
• Directory of Open Access Journals (DOAJ): indexes thousands of diamond OA journals.

Advantages of diamond open access:

• equity & inclusivity: removes financial barriers for authors or readers;
• immediate & global access: maximizes the reach and impact of research;
• author rights: authors retain copyright and can freely share their work;
• community control: academic communities manage publishing standards and content quality.

Challenges of diamond open access:

• sustainability: long-term funding relies on external grants and institutional support;
• limited infrastructure: many diamond OA journals lack the resources of commercial publishers;
• visibility issues: may not always be indexed in high-profile databases like Web of Science or Scopus.

The table below compares the three open access models.

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Open Access Network (2024). Green, Gold, and Diamond Open Access. [tiešsaiste] [skatīts 18/02/2025]. Pieejams: https://open-access.network/en/information/open-access-primers/green-and-gold (CC-BY)

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