‘Green’ OA involves the author placing an article in an online repository where it can be accessed free of charge. These repositories can be subject-based, such as bioRxiv, or institutional, such as the Open University’s Open Research Online (ORO). Both subscription and OA articles (for example from a ‘gold’ journal) can be placed in a repository.

A comprehensive list of Green OA repositories can be found in the Directory of Open Access Repositories (OpenDOAR).

Articles can be placed in repositories either as ‘preprints’ (before submission to a journal) or ‘postprints’ (after peer review but before publication). It may also be possible to deposit a pdf version of the final published article. Journals have different policies regarding which versions can be placed in repositories, which you can check this using the SHERPA/RoMEO tool.  

Publishers may enforce an embargo period following publication, before an article can be placed in a repository. However, research funders may require a different embargo period as part of the funding mandate, so do check if this is the case. If your research is funded by a major UK funding body (e.g. NERC), the SHERPA/FACT tool can check compliance with research funders regarding acceptable versions and embargoes.

Academic Social Networks (ASNs) such as ResearchGate are a popular channel to share published articles. However, posting on them may break copyright rules, particularly when final version pdfs are uploaded⁵. There are no checks for copyright compliance before articles are hosted¹ and it is possible that a sizeable proportion of articles shared on ResearchGate do not comply with publisher policies⁵.

Take care if you are planning to share your article via an ASN. Check that you are complying with publisher policies before sharing articles on ASNs to avoid going down the ‘Black’ (illegal) OA route.

Another form of ‘Black’ OA is where articles are shared through illegal sites such as SciHub. In this case the articles are ‘mined’ directly from publishers’ websites, without the consent of authors or publishers⁶, so is something an author has no control over.