deep web

The Deep Web, also called the Invisible Web, Dark Web, Darknet or Hidden Web, comprises the part of the Internet that cannot be found via search engines and is thus not covered. The reasons for this are primarily that certain website content is not freely accessible and certain websites are not indexed by conventional search engines.

The Invisible Web consists of specialized databases, of dictionaries, digital libraries, specialized archives, sensitive private and health data, e-books and other specialized literature. It is estimated that the size of the Deep Web is approximately 500 times that of the Visible Web. The web pages of the Deep Web are accessed via the Internet, but without search engine support.

In contrast to the Invisible or Deep Web is the Visible Web or also called Surface Web. This "visible" part of the Internet is covered by search engines and the pages of the Visible Web are indexed. It is assumed that the part of the Internet that is invisible to search engines is significantly larger than the visible part.