Definitions[]
The Deep Web (also called the Invisible Web, Undernet, and the Hidden Web)
| “ | is online content that cannot be found by search engines. These are pages that are either located too "deep" in a website for a search engine to find them, are pages that a search engine cannot index because it technically is unable to do so, or are pages that a search engine cannot access because they are password protected. | ” |
| “ | denote[s] a class of content on the Internet that, for various technical reasons, is not indexed by search engines.[1] | ” |
| “ | is 'a class of content on the Internet' that, for various technical reasons, is not indexed by search engines, and thus would not be accessible through a traditional search engine.[2] | ” |
Overview[]
Search engines rely on technology that generally identifies "static" pages, rather than the "dynamic" information stored in databases. Deep Web content resides in searchable databases, the results from which can only be discovered by a direct query. Without the direct query, the database does not publish the result. Thus, while the content is there, it is skipped over by traditional search engines which cannot probe beneath the surface.
"Information on the deep Web is 400 to 550 times larger than the commonly defined World Wide Web."[3]
The furthest corners of the Deep Web, known as the Dark Web, contain content that has been intentionally concealed.