Open access (OA) refers to online research outputs that are free of all restrictions on access (e.g., access tolls) and free of many restrictions on use (e.g. certain copyright and license restrictions). 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, and monographs.

Two degrees of open access can be distinguished: gratis open access, which is online access free of charge, and libre open access, which is online access free of charge plus various additional usage rights. These additional usage rights are often granted through the use of various specific Creative Commons licenses. Libre open access is equivalent to the definition of open access 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.

There are multiple ways authors can provide open access to their work. One way is to publish it and then self-archive it in a repository where it can be accessed for free, such as their institutional repository, or a central repository such as PubMed Central. This is known as 'green' open access. Some publishers require delays, or an embargo, on when a research output in a repository may be made open access. Several initiatives provide an alternative to the American and English language dominance of existing publication indexing systems, including Index Copernicus, SciELO and Redalyc.

In the context of infrastructure, open access involves physical infrastructure such as railways and physical telecommunications network plant being made available to clients other than the owners, for a fee.

For example, private railways within a steel works are private and not available to outsiders. In the hypothetical case of the steelworks having a port or a railway to a distant mine, outsiders might want access to save having to incur a possibly large cost of building their own facility.

Marconi and radio communication

The Marconi Company was a pioneer of long distance radio communication, which was particularly useful for ships at sea. Marconi was very protective about its costly infrastructure and refused - except for emergencies - to allow other radio companies to share its infrastructure. Even if the message sender was royalty, as in the Deutschland incident of 1902, they continued to refuse access. Since radio communication was so new, it preceded laws, regulations and licences, which might otherwise imposed conditions to open infrastructure to other players.

Open access is unrestricted online access to peer-reviewed scholarly research.

Open access may also refer to:

Computing, Internet and communication

Other uses