Open access (OA) is a set of principles and a range of practices through which nominally copyrightable publications are delivered to readers free of access charges or other barriers. With open access strictly defined (according to the 2001 definition), or libre open access, barriers to copying or reuse are also reduced or removed by applying an open license for copyright, which regulates post-publication uses of the work.
The main focus of the open access movement has been on peer reviewed research literature, and more specifically on academic journals. This is because:
such publications have been a subject of serials crisis, unlike newspapers, magazines and fiction writing. The main difference between these two groups is in demand elasticity: whereas an English literature curriculum can substitute Harry Potter and the Philosopher's Stone with a public domain alternative, such as A Voyage to Lilliput, an emergency room physician treating a patient for a life-threatening urushiol poisoning cannot substitute the most recent, but paywalled review article on this topic with a 90-year-old copyright-expired article that was published before the invention of prednisone in 1954.
the authors of research papers are not paid in any way, so they do not suffer any monetary losses, when they switch from behind paywall to open access publishing, especially, if they use diamond open access media.
the cost of electronic publishing, which has been the main form of distribution of journal articles since , is incommensurably smaller than the cost of on-paper publishing and distribution, which is still preferred by many readers of fiction.
Whereas non-open access journals cover publishing costs through access tolls such as subscriptions, site licenses or pay-per-view charges, open-access journals are characterised by funding models which do not require the reader to pay to read the journal's contents, relying instead on author fees or on public funding, subsidies and sponsorships. Open access can be applied to all forms of published research output, including peer-reviewed and non peer-reviewed academic journal articles, conference papers, theses, book chapters, monographs, research reports and images.
Definitions There are different models of open access publishing and publishers may use one or more of these models.
Colour naming system Different open access types are currently commonly described using a colour system. The most commonly recognised names are "green", "gold", and "hybrid" open access; however, several other models and alternative terms are also used.
Gold OA In the gold OA model, the publisher makes all articles and related content available for free immediately on the journal's website. In such publications, articles are licensed for sharing and reuse via Creative Commons licenses or similar. Many gold OA publishers charge an article processing charge (APC), which is typically paid through institutional or grant funding. The majority of gold open access journals charging APCs follow an "author-pays" model, although this is not an intrinsic property of gold OA.
Green OA
Self-archiving by authors is permitted under green OA. Independently from publication by a publisher, the author also posts the work to a website controlled by the author, the research institution that funded or hosted the work, or to an independent central open repository, where people can download the work without paying.
Green OA is free of charge for the author. Some publishers (less than 5% and decreasing as of 2014) may charge a fee for an additional service such as a free license on the publisher-authored copyrightable portions of the printed version of an article.
If the author posts the near-final version of their work after peer review by a journal, the archived version is called a "postprint". This can be the accepted manuscript as returned by the journal to the author after successful peer review.
Hybrid OA Hybrid open-access journals contain a mixture of open access articles and closed access articles. A publisher following this model is partially funded by subscriptions, and only provide open access for those individual articles for which the authors (or research sponsor) pay a publication fee. Hybrid OA generally costs more than gold OA and can offer a lower quality of service. A particularly controversial practice in hybrid open access journals is "double dipping", where both authors and subscribers are charged. For these reasons, hybrid open access journals have been called a "Mephistophelian invention", and publishing in hybrid OA journals often do not qualify for funding under open access mandates, as libraries already pay for subscriptions thus have no financial incentive to fund open access articles in such journals.
Bronze OA Bronze open access articles are free to read only on the publisher page, but lack a clearly identifiable license. Such articles are typically not available for reuse.
Diamond/platinum OA
Journals that publish open access without charging authors article processing charges are sometimes referred to as diamond or platinum OA. Since they do not charge either readers or authors directly, such publishers often require funding from external sources such as the sale of advertisements, academic institutions, learned societies, philanthropists or government grants. There are now over 350 platinum OA journals with impact factors over a wide variety of academic disciplines, giving most academics options for OA with no APCs. Diamond OA journals are available for most disciplines, and are usually small (<25 articles per year) and more likely to be multilingual (38%); thousands of such journals exist.
Black OA
The growth of unauthorized digital copying by large-scale copyright infringement has enabled free access to paywalled literature. This has been done via existing social media sites (e.g. the #ICanHazPDF hashtag) as well as dedicated sites (e.g. Sci-Hub). In some ways this is a large-scale technical implementation of pre-existing practice, whereby those with access to paywalled literature would share copies with their contacts. However, the increased ease and scale from 2010 onwards have changed how many people treat subscription publications.
Gratis and libre
Similar to the free content definition, the terms 'gratis' and 'libre' were used in the Budapest Open Access Initiative definition to distinguish between free to read versus free to reuse.
Gratis open access () refers to free online access, to read, free of charge, without re-use rights.
Libre open access () also refers to free online access, to read, free of charge, plus some additional re-use rights, covering the kinds of open access defined in the Budapest Open Access Initiative, the Bethesda Statement on Open Access Publishing and the Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities. The re-use rights of libre OA are often specified by various specific Creative Commons licenses; all of which require as a minimum attribution of authorship to the original authors. In 2012, the number of works under libre open access was considered to have been rapidly increasing for a few years, though most open-access mandates did not enforce any copyright license and it was difficult to publish libre gold OA in legacy journals. However, there are no costs nor restrictions for green libre OA as preprints can be freely self-deposited with a free license, and most open-access repositories use Creative Commons licenses to allow reuse.>
FAIR
FAIR is an acronym for 'findable, accessible, interoperable and reusable', intended to more clearly define what is meant by the term 'open access' and make the concept easier to discuss. Initially proposed in March 2016, it has subsequently been endorsed by organisations such as the European Commission and the G20. Note, however, that FAIR principles include "A1.2: The protocol allows for an authentication and authorisation procedure where necessary." This means that a FAIR dataset may be either closed (restricted access) or open (no access restrictions). So, only FAIR data without access restrictions are open access.
Features
The emergence of open science or open research has brought to light a number of controversial and hotly-debated topics.
Scholarly publishing invokes various positions and passions. For example, authors may spend hours struggling with diverse article submission systems, often converting document formatting between a multitude of journal and conference styles, and sometimes spend months waiting for peer review results. The drawn-out and often contentious societal and technological transition to Open Access and Open Science/Open Research, particularly across North America and Europe (Latin America has already widely adopted "Acceso Abierto" since before 2000) has led to increasingly entrenched positions and much debate.
The area of (open) scholarly practices increasingly sees a role for policy-makers and research funders giving focus to issues such as career incentives, research evaluation and business models for publicly funded research. Plan S and AmeliCA (Open Knowledge for Latin America) caused a wave of debate in scholarly communication in 2019 and 2020.
Licenses
Subscription-based publishing typically requires transfer of copyright from authors to the publisher so that the latter can monetise the process via dissemination and reproduction of the work. With OA publishing, typically authors retain copyright to their work, and license its reproduction to the publisher. Retention of copyright by authors can support academic freedoms by enabling greater control of the work (e.g. for image re-use) or licensing agreements (e.g. to allow dissemination by others).
The most common licenses used in open access publishing are Creative Commons. The widely used CC BY license is one of the most permissive, only requiring attribution to be allowed to use the material (and allowing derivations and commercial use). A range of more restrictive Creative Commons licenses are also used. More rarely, some of the smaller academic journals use custom open access licenses. Some publishers (e.g. Elsevier) use "author nominal copyright" for OA articles, where the author retains copyright in name only and all rights are transferred to the publisher.
Funding Since open access publication does not charge readers, there are many financial models used to cover costs by other means. Open access can be provided by commercial publishers, who may publish open access as well as subscription-based journals, or dedicated open-access publishers such as Public Library of Science (PLOS) and BioMed Central. Another source of funding for open access can be institutional subscribers. One example is the Subscribe to Open publishing model introduced by Annual Reviews; if the subscription revenue goal is met, the given journal's volume is published open access. The number of journals implementing this model grew from 192 in 2024 to 378 in 2025.
Advantages and disadvantages of open access have generated considerable discussion amongst researchers, academics, librarians, university administrators, funding agencies, government officials, commercial publishers, editorial staff and society publishers. Reactions of existing publishers to open access journal publishing have ranged from moving with enthusiasm to a new open access business model, to experiments with providing as much free or open access as possible, to active lobbying against open access proposals. There are many publishers that started up as open access-only publishers, such as PLOS, Hindawi Publishing Corporation, Frontiers in... journals, MDPI and BioMed Central.
Article processing charges