Open access (OA) publishing makes peer-reviewed research freely available online — no subscription, no paywall. The three main models are Gold OA (author pays to publish immediately free), Green OA (author self-archives a version in a repository), and Diamond OA (free for both authors and readers, funded institutionally). Each model has distinct cost implications, timelines, and equity outcomes for the global research community.
KEY TAKEAWAYS:
- Open access removes subscription paywalls, making research readable by anyone worldwide.
- Gold OA: publisher makes the article free immediately — usually in exchange for an Article Processing Charge (APC) paid by the author or funder.
- Green OA: authors self-archive a version (preprint or postprint) in a public repository, often after an embargo period.
- Diamond OA: no fees for authors or readers — journals are funded through institutions, grants, or societies.
- APCs under Gold OA can reach thousands of dollars, creating new barriers for researchers in low-income settings.
- Mandates from funders (NIH, Wellcome Trust, UKRI) are accelerating OA adoption globally.
- Choosing the right model depends on funder requirements, budget, and the publisher’s self-archiving policy.
What Is Open Access Publishing?
Open access (OA) publishing is a model of scholarly communication in which peer-reviewed research is made freely available online — without subscription fees, access paywalls, or copyright restrictions that prevent reuse.
The term covers a spectrum of approaches. What they share is a commitment to the principle that publicly funded research should be publicly available. What differs is who pays the costs of publication, when access begins, and where the final article is hosted.
Open access began gaining traction in the early 2000s as a response to rapidly rising journal subscription costs. The landmark Budapest Open Access Initiative (2002), followed by the Berlin Declaration (2003), established its foundational principles and set the OA movement in motion.
Why Open Access Matters: Barriers the Traditional System Created
Under the traditional subscription model, journal access is gated behind institutional licences. Researchers at well-funded universities in wealthy countries get full access. Researchers at under-resourced institutions — or independent scholars, clinicians in the Global South, and the public — do not.
The consequences are real:
- Scientific findings remain siloed, slowing the pace of discovery.
- Duplicate research gets conducted because previous results are inaccessible.
- Knowledge produced with public funding stays behind private paywalls.
- Collaboration across institutional and geographic boundaries is harder than it needs to be.
Open access addresses these problems directly. It increases the discoverability of research, encourages cross-disciplinary work, and lowers the cost of staying current in a field — regardless of where a researcher is located.
The Three Core Open Access Models
Most paths to open access fall into one of three categories. Understanding each helps authors, institutions, and publishers make the right publishing decisions.
1. Gold Open Access
Gold OA makes the final, publisher-formatted version of an article freely available immediately upon publication — directly on the publisher’s website.
The trade-off: someone has to cover the cost of publication. In most Gold OA journals, that means an Article Processing Charge (APC) paid by the author, their institution, or their research funder.
- APCs typically range from a few hundred to over $10,000 depending on the journal and publisher.
- Authors generally retain copyright and publish under a Creative Commons licence (commonly CC BY).
- Major publishers operating Gold OA journals include PLOS, BioMed Central, and Frontiers.
- Hybrid journals allow Gold OA for individual articles within an otherwise subscription-based journal.
APC affordability is a significant equity issue. Researchers from lower-income countries, early-career academics, and those without institutional funding support may be effectively excluded from Gold OA — replacing one barrier (access to read) with another (access to publish).
2. Green Open Access (Self-Archiving)
Green OA allows authors to deposit a version of their article in a publicly accessible repository — typically an institutional repository, a subject-based archive like PubMed Central or arXiv, or a personal website.
- The deposited version is usually a preprint (before peer review) or an accepted manuscript (post-peer-review, pre-typesetting).
- Many publishers impose an embargo period — typically 6 to 24 months — before the manuscript can be made publicly available.
- Authors can check publisher self-archiving policies via SHERPA/RoMEO, a free online tool.
- Green OA involves no APC — making it a cost-free route to open availability.
The limitation of Green OA is that the deposited version is typically not the final typeset article. For readers and researchers needing exact citations, the version of record matters. Embargo periods also delay access — sometimes significantly.
3. Diamond Open Access
Diamond OA is a publishing model in which neither authors nor readers pay. Journals are sustained through institutional funding, grants, library consortia, scholarly societies, or volunteer labour.
- Diamond OA is considered the most equitable model — removing financial barriers on both sides of the publishing relationship.
- It is particularly common in humanities, social sciences, and small disciplinary communities.
- UNESCO launched the Global Diamond Open Access Alliance in 2024 to strengthen and scale the model.
- The EU Council (2023) has recommended promoting diamond OA as part of European research policy.
The challenge is sustainability. Diamond OA journals often rely on volunteer editorial work and short-term institutional support. A 2024 analysis found that diamond journals are significantly underrepresented in major indexing services like Scopus and Web of Science compared to their Gold OA counterparts — which can affect the visibility and citation impact of published work.
Comparing the Three Models at a Glance
| Feature | Gold OA | Green OA | Diamond OA |
|---|---|---|---|
| Access Timing | Immediate on publication | After embargo period | Immediate on publication |
| Publication Fee (Author) | APC paid by author/funder | No APC charged | No APC charged |
| Access Fee (Reader) | No subscription required | No subscription required | No subscription required |
| Version Available | Final published version | Preprint or accepted manuscript | Final published version |
| Copyright | Retained by author (CC licence) | Varies by publisher policy | Retained by author (CC licence) |
| Funding Model | APC revenue to publisher | Permitted under publisher policy | Institutional grants or society funding |
Funder Mandates: Who Is Driving OA Adoption?
Open access is no longer just an ideal — it is increasingly a legal or contractual requirement imposed by research funders.
- NIH (USA): The 2023 updated Public Access Policy requires immediate open access for all NIH-funded research.
- Wellcome Trust (UK): Requires Gold OA with CC BY licence for all funded publications.
- UKRI (UK Research and Innovation): Mandates open access for peer-reviewed journal articles arising from UKRI funding.
- European Commission / Horizon Europe: Requires open access for all funded research; supports Plan S principles.
- Plan S (cOAlition S): A coalition of funders requiring immediate, full open access — no embargo, no hybrid journal exceptions.
Publishers and institutions have responded with Transformative Agreements — deals between libraries and publishers that bundle subscription access with open access publishing credits, helping institutions manage APC costs at scale.
Open Access and the Peer-Review Question
A persistent concern about open access is whether the APC model creates incentives for publishers to accept more papers — compromising peer review standards to generate revenue.
This concern has merit in some contexts. Predatory journals — which charge APCs while providing little or no genuine peer review — remain a known problem in the OA ecosystem. Researchers are advised to verify journals via the Directory of Open Access Journals (DOAJ) and to consult their institution’s library for guidance on reputable publishers.
Reputable Gold OA publishers like PLOS, BioMed Central, and Oxford University Press maintain rigorous editorial standards equivalent to their subscription-based counterparts. Diamond OA journals are typically run by scholarly communities with strong intrinsic motivation to maintain quality.
Practical Guide: Choosing the Right Open Access Route
For researchers navigating their options, the following steps provide a useful framework:
- Check your funder’s OA policy. Many funders specify the required model, licence type, and embargo limits.
- Check your publisher’s self-archiving policy on SHERPA/RoMEO if considering Green OA.
- Assess APC costs and available funding. Some institutions have OA funds or Transformative Agreement credits.
- Look for fee waivers. Many Gold OA publishers offer full or partial APC waivers for researchers from low-income countries.
- Consider Diamond OA journals in your discipline — particularly if APC costs are prohibitive.
- Verify journal quality via the DOAJ before submitting to an unfamiliar OA journal.
The Future of Open Access
The direction of travel is clear: open access will become the default mode of scholarly publishing. Whether the path leads primarily through Gold, Green, or Diamond models — or some combination — will depend on how funders, governments, publishers, and institutions navigate the economic and structural challenges ahead.
Diamond OA represents the most equitable vision of open science: no cost barriers on either side. But scaling it requires sustained institutional commitment, shared infrastructure, and indexing visibility. Gold OA offers immediate access and broad publisher adoption but risks entrenching financial inequality in who can publish.
For academic publishers and publishing services providers, the open access transition demands both technical adaptation and strategic clarity about which models to support and how to serve authors navigating an increasingly complex landscape.
Frequently Asked Questions
What is open access publishing?
Open access (OA) publishing is a model in which peer-reviewed academic research is made freely available online — without subscription fees or access restrictions. Readers anywhere can read, download, and reuse the content. Costs are typically covered by authors, institutions, funders, or societies, rather than by readers paying per article or subscription.
What is the difference between Gold and Green Open Access?
Gold OA makes the final published version of an article freely available immediately on the publisher’s website. Authors (or their institutions/funders) typically pay an Article Processing Charge (APC). Green OA allows authors to self-archive a version of their article — usually a preprint or accepted manuscript — in a public repository, often after an embargo period set by the publisher. Green OA is generally free for authors.
What is Diamond Open Access?
Diamond OA is a publishing model in which neither authors nor readers pay fees. Journals are funded through institutional support, government grants, scholarly societies, or volunteer work. It is considered the most equitable model in terms of removing financial barriers to both publishing and reading research.
Do I have to pay to publish open access?
It depends on the model. Gold OA typically requires an Article Processing Charge (APC), which can range from a few hundred to over $10,000. Green OA is generally free — you simply deposit a version of your article in a repository. Diamond OA journals are free for authors. Some Gold OA journals offer waivers for researchers from low-income countries or those without institutional funding.
What is an APC in academic publishing?
An Article Processing Charge (APC) is a fee paid by the author or their institution to a publisher to make an article freely available immediately after publication under open access. APCs are the primary revenue model for Gold OA journals and are also used in hybrid journals that offer open access as an option.
What are the main challenges of open access?
The main challenges include: APCs creating financial barriers for researchers without institutional funding; sustainability of Diamond OA journals that rely on volunteer labour and short-term grants; variable embargo lengths in Green OA delaying access; and the underrepresentation of Diamond OA journals in major indexing services. Predatory journals remain an ongoing concern across the OA ecosystem.
