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Deep web

technology Maturity 11-13 Next article →

The internet is much larger than most people realize. Most users interact with the surface web. This is the part of the World Wide Web that anyone can access using standard search engines. However, a massive portion of the internet remains hidden from these search tools. This area is known as the deep web. It is also sometimes called the invisible web or the hidden web. The deep web consists of all web content that is not indexed by standard search-engine programs.

This means that while the information exists, a regular search for it will not bring it up.

To understand the deep web, you must understand how search engines work. They use programs called web crawlers to find information. These crawlers follow hyperlinks from one page to another. This process is ideal for the surface web. However, it is often ineffective for the deep web. One reason is unlinked content. These are pages that do not have backlinks, which are links from other pages. If no other page links to a site, a crawler might never find it.

Another reason involves dynamic content. These are pages that change based on a user's specific request. For example, a page might only appear after someone submits a form or a database query. Because there are an infinite number of possible queries, a crawler cannot guess them all.

There are many different ways content becomes part of the deep web. Some sites use limited access content to stay hidden. They might use the Robots Exclusion Standard or CAPTCHAs to stop search engines from browsing them. Other content is simply non-HTML or non-text content. This includes information hidden inside video or image files. Some content is also scripted. This means the page only works through specific software like JavaScript, Flash, or Ajax.

Finally, there is the private web. These are sites that require a registration and a login. This includes your personal web mail, online banking, and cloud storage. Even paywalled services, like certain online newspapers, are part of the deep web.

People have been naming and studying these hidden layers for decades. In 1994, Jill Ellsworth used the term "Invisible Web" for sites not registered with search engines. In 1996, Frank Garcia also used this term. Later that year, Bruce Mount and Matthew B. Koll released a program called @1. This program was a deep web tool that contained 5.7 terabytes of content. At that time, that was 30 times the size of the entire World Wide Web.

The term "deep web" as we use it today was introduced by computer scientist Michael K. Bergman in 2001. He used it specifically as a search-indexing term.

It is very important to distinguish the deep web from the dark web. Many people use these terms as if they mean the same thing, but they are different. The deep web is simply anything not indexed by a search engine. The dark web is a specific, smaller portion of the deep web. It is hidden intentionally. You cannot reach the dark web using a standard web browser. Instead, you must use special software like Tor or I2P. Tor allows users to access websites with a .onion address anonymously. While the deep web contains many helpful tools like banking, the dark web is often associated with illegal activities.

Researchers have developed many ways to explore these hidden areas. In 2001, Sriram Raghavan and Hector Garcia-Molina created a model for a hidden-web crawler. This crawler used terms provided by users to navigate web forms. Other researchers, such as those at UCLA, created crawlers that automatically generate queries to search forms. Even commercial search engines like Google have found ways to help. Google uses the Sitemap Protocol to allow web servers to advertise their URLs. This helps engines discover resources that are not directly linked to the surface web.

Today, the deep web is a vital part of our digital lives. It connects us to secure services and vast amounts of data. Web archives, like the Wayback Machine, are also considered deep web content. These archives allow us to see versions of websites from the past. Since search engines cannot index these old versions, they remain part of the deep web. As technology grows, the distinction between the surface and the deep web continues to shape how we navigate the digital world.

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