Open access (OA) refers to the practice of providing unrestricted access to scholarly research articles online, enabling anyone to read, download, and distribute them without subscription fees or paywalls. This approach aims to democratize knowledge dissemination by removing financial and access barriers, and ensuring that research findings are freely available to researchers, practitioners, and the general public. The overarching goal of open access is to enhance the visibility, usage, and impact of research by making it accessible to a global audience, fostering greater collaboration and advancement in various fields of study.
| Type | Description | Funding | Licensing |
| Gold Open Access | Articles are freely accessible on the publisher’s website immediately upon publication. | Often funded by Article Processing Charges (APCs) paid by the authors or their institutions. | Typically published under a Creative Commons (CC) license, allowing varying degrees of reuse. |
| Green Open Access | Authors can self-archive a version of their article (pre-print or post-print) in a repository or on their personal website. | No direct cost to the author, but the final published version is usually behind a paywall. | The self-archived version may have restrictions imposed by the publisher’s policy. |
| Bronze Open Access | Articles are freely accessible on the publisher’s website, but without a clear license for reuse. | Typically no direct cost to the author, and the publisher may decide to make articles freely available for a limited time or as a promotional offer. | No explicit open license, which can limit reuse and redistribution. |
| Hybrid Open Access | Traditional subscription-based journals that offer an option for authors to make individual articles open access by paying an APC. | APCs are paid by the author or their institution for the open access option. | Articles made open access are usually under a Creative Commons license. |
| Diamond/Platinum Open Access | Articles are freely accessible with no cost to authors or readers. These journals are typically funded by institutions, societies, or grants. | Supported by academic institutions, funding agencies, or other organizations. | Generally published under a Creative Commons license, promoting wide reuse. |
| Libre Open Access | Articles are freely accessible and can be reused and redistributed with minimal restrictions, often under a Creative Commons license. | Can vary; may involve APCs or institutional funding. | Explicit licenses that allow for free use and distribution, usually Creative Commons. |
| Delayed Open Access | Articles become freely accessible after an embargo period set by the publisher. | No APCs for authors, but initial access is limited to subscribers. | Varies, but often no open license during the embargo period. |
| Public Access | Similar to open access but often refers to works funded by government grants that must be made publicly accessible. | Typically government-funded research. | Often under public access policies, which may not always include Creative Commons licenses. |
| Repository Open Access | Articles are deposited in open access repositories (institutional or subject-specific) and made freely accessible. | No direct cost to authors, supported by institutions or grants. | Varies based on repository policies, but often allows some form of reuse. |
Many funding agencies require that recipients of public funding for research purposes need to post their publications and findings on OA platforms to be publicly accessible. For example, in the US, NIH funding requires publication to PubMed no later than 12 months after the official date of publication. See NIH Public Access Policy implements Division F Section 217 of PL 111-8 (Omnibus Appropriations Act, 2009). In Europe, Plan S requires immediate publication in OA journals or platforms. See https://www.coalition-s.org/.