Deep Web

The deep web,[1] invisible web,[2] or hidden web[3] are parts of the World Wide Web whose contents are not indexed by standard web search engines. The opposite term to the deep web is the surface web, which is accessible to anyone using the Internet.[4] Computer scientist Michael K. Bergman is credited with coining the term deep web in 2001 as a search indexing term.[5]

The content of the deep web is hidden behind HTTP forms[6][7] and includes many very common uses such as web mail, online banking, and services that users must pay for, and which are protected by paywalls, such as video on demand and some online magazines and newspapers.

The content of the deep web can be located and accessed by a direct URL or IP address, and may require a password or other security access past the public website page.

Terminology
The first conflation of the terms "deep web" with "dark web" came about in 2009 when deep web search terminology was discussed together with illegal activities taking place on the Freenet and darknet.[8]

Since then, after their use in the media's reporting on the Silk Road, many[9][10] people and media outlets have taken to using 'deep web' synonymously with the dark web or darknet, a comparison some reject as inaccurate[11] and consequently has become an ongoing source of confusion.[12] Wired reporters Kim Zetter[13] and Andy Greenberg[14] recommend the terms be used in distinct fashions. While the deep web is a reference to any site that cannot be accessed through a traditional search engine, the dark web is a portion of the deep web that has been intentionally hidden and is inaccessible through standard browsers and methods.[15][16][17][18][19]

Non-indexed content
Bergman, in a paper on the deep web published in The Journal of Electronic Publishing, mentioned that Jill Ellsworth used the term Invisible Web in 1994 to refer to websites that were not registered with any search engine.[20] Bergman cited a January 1996 article by Frank Garcia:[21]

It would be a site that's possibly reasonably designed, but they didn't bother to register it with any of the search engines. So, no one can find them! You're hidden. I call that the invisible Web.

Another early use of the term Invisible Web was by Bruce Mount and Matthew B. Koll of Personal Library Software, in a description of the #1 Deep Web tool found in a December 1996 press release.[22]

The first use of the specific term deep web, now generally accepted, occurred in the aforementioned 2001 Bergman study.[20]