Open access (OA) means unrestricted online access to research. 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,[2] book chapters,[3] and monographs.[4]
Open access comes in two degrees: gratis open access, which is online access free of charge, and libre open access, which is online access free of charge and with some additional usage rights.[5] These additional usage rights are often granted through the use of various specific Creative Commons licenses.[6] Only libre open access is fully compliant with definitions of open access such as the Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities.
Two of the ways authors can provide open access are (1) by self-archiving their journal articles in an open access repository, also known as 'green' open access, or (2) by publishing in an open access journal, known as 'gold' open access.[7] With green open access[8][9] authors publish in any journal and then self-archive a version of the article for gratis public use in their institutional repository,[10][11] in a central repository (such as PubMed Central), or on some other open access website. With gold open access, authors publish in open access journals,[12] which provide immediate open access to all of their articles, usually on the publisher's website.[13] Hybrid open access journals are subscription journals that provide gold open access only for those individual articles for which their authors (or their author's institution or funder) pay an open access publishing fee.[14]
Widespread public access to the World Wide Web in the late 1990s and early 2000s fueled the open access movement, and prompted both the green open access self-archiving of non-open access journal articles and the creation of gold open access journals. Conventional non-open access journals cover publishing costs through access tolls such as subscriptions, site licenses or pay-per-view. Some non-open access journals provide open access after an embargo period of 6–12 months or longer (see delayed open access journals).[14] Active debate over the economics and reliability of various ways of providing open access continues among researchers, academics, librarians, university administrators, funding agencies, government officials, commercial publishers, editorial staff and society publishers.