Glossary
Dark web
The dark web is the small part of the internet made of sites that need special software — usually Tor Browser — to reach.
What it means
The dark web is the small part of the internet made of sites that need special software — usually Tor Browser — to reach. It is not a separate internet and not a place in the physical sense: it is a set of websites whose addresses end in .onion and which live on top of the Tor network. It contains a mix of the ordinary, the secretive and the criminal, in proportions nobody can honestly measure — and most of what is said about it in headlines is exaggerated or simply wrong.
How it works
Dark web sites are onion services: they meet visitors inside the Tor network, so neither side learns the other's address. Their addresses are long strings ending in .onion, derived from the service's cryptographic key, which is why they look random and cannot be chosen freely. The dark web sits inside the deep web — everything search engines do not index — but it is only a small part of it. Most of the deep web is ordinary: your email, your online banking, paywalled articles, private company databases. The surface web is the public part that search engines do index. Those three layers are the vocabulary you need before any dark web claim makes sense.
Example
Imagine a fictional researcher, Dr. Aisha, studying how whistleblowing tools work. She reads about a secure drop-box for journalists that lives as an onion service. To reach it she needs Tor Browser, and the address is a long string ending in .onion — she cannot find it through a search engine, and she cannot type it into an ordinary browser. That is the dark web in one scene: a small, hidden corner reachable only with special software, used here for a legitimate purpose that has nothing to do with crime. The same technology is also used for criminal marketplaces — and the honest fact is that both exist, and nobody can give you a true percentage split.
Common misunderstandings
The myths are the subject of a whole lesson on this site, but the three biggest are worth stating here: that the dark web is 95 percent of the internet (it traces to a 2001 estimate, not a measurement); that it is mostly illegal marketplaces (nobody can measure the proportions); and that hitman services advertised there are real businesses (they are documented scams). Each myth survives because it is repeated more often than it is checked.
Related terms
Learn more
- What is the dark web?
- What is on the dark web?
- Common dark web myths
- Dark Web Fundamentals Path
- Back to the full glossary
Last checked: 14 November 2026.
Frequently asked questions
Is visiting the dark web illegal?
In most countries, simply visiting is not a crime — but criminal activity there is a crime everywhere. Whether it is illegal depends on where you are and what you do. This is general information, not legal advice.
How big is the dark web?
Nobody can say with confidence, because dark web sites are not indexed by search engines and are designed not to be counted. The famous percentages come from a 2001 estimate and have no current basis. Any site that gives you a confident size figure is guessing.
Why do dark web addresses look random?
Because a .onion address is derived from the service's cryptographic key, not chosen freely. The address is a fingerprint of the key — which is why it looks like a random string, and why an address proves you reached the service that holds that key.