Deep web

The deep web, also known as the invisible web or hidden web, refers to content on the World Wide Web that is not indexed by standard search engines. This is primarily due to a variety of technical reasons that prevent search engine crawlers from accessing and indexing the information. It's distinct from the dark web, which is a deliberately concealed part of the deep web used for both legitimate and illicit activities.

Content within the deep web is typically hidden behind password protection, requires specific software or configurations, or is dynamically generated through queries. Examples include online banking portals, email inboxes, secure document repositories, academic databases, and paywalled content. These resources are intentionally excluded from search engine indexing to protect user privacy, maintain security, or control access.

The size of the deep web is significantly larger than the surface web, the portion of the internet indexed by search engines. Estimates vary widely, but it's generally accepted that the deep web contains a substantial amount of data.

Accessing the deep web often requires specific credentials, login information, or navigation through a specific website or database. It is not inherently malicious, and much of its content is perfectly legal and commonplace.

The term "deep web" should not be confused with the "dark web," which is a small subset of the deep web that utilizes overlay networks and encryption technology to anonymize users and activities. While the deep web includes many legitimate uses, the dark web is often associated with illegal marketplaces, criminal activities, and content that is intentionally hidden from public view.