Some journals are 'born digital' in that they are solely published on the web and in a digital format, but most electronic journals originated as print journals, which subsequently evolved to have an electronic version, while still maintaining a print component. As academic research habits have changed in line with the growth of the internet, the e-journal has come to dominate the journals world.
An e-journal closely resembles a print journal in structure: there is a table of contents which lists the articles, and many electronic journals still use a volume/issue model, although some titles now publish on a continuous basis. Online journal articles are a specialized form of electronic document: they have the purpose of providing material for academic research and study, and they are formatted approximately like journal articles in traditional printed journals. Often a journal article will be available for download in two formats - as a PDF and in HTML format, although other electronic file types are often supported for supplementary material. Articles are indexed in bibliographic databases, as well as by search engines. E-journals allow new types on content to be included in journals, for example video material, or the data sets on which research has been based.
With the growth and development of the internet, there has been a growth in the number of new journals, especially in those that exist as digital publications only. A subset of these journals exist as Open Access titles, meaning that they are free to access for all, and have Creative Commons licences which permit the reproduction of content in different ways. High quality open access journals are listed in Directory of Open Access Journals. Most however continue to exist as subscription journals, for which libraries, organisations and individuals purchase access.