What is the dark web? How it works and what's really there

The dark web is the part of the web made of sites that can only be reached through special anonymity networks, the best known being Tor. Those networks hide both where a site's server is and who is visiting it, by bouncing traffic through several volunteer-run computers in layers of encryption. The dark web is tiny compared with the ordinary web. It hosts criminal markets, but also news sites, whistleblowing services and people avoiding censorship.

In short

• The deep web is anything search engines can't see, like your email inbox. The dark web is a small corner of it that needs special software to reach.
• Tor hides who is talking to whom by wrapping traffic in three layers of encryption and passing it through three relays, none of which sees the whole path.
• Anonymity cuts both ways: it protects journalists and dissidents, and it shelters scams and illegal trade.

Is the dark web the same as the deep web?

No, and mixing them up is the most common mistake about the subject. The World Wide Web can be split three ways:

	Surface web	Deep web	Dark web
What it is	Pages search engines index	Pages search engines can't reach	Sites reachable only through an anonymity network
Examples	News sites, Wikipedia, shop pages	Your email, bank account, medical records, company intranets, paywalled articles	Onion sites on Tor, including some news outlets, forums and markets
How you reach it	Any browser, any search	Any browser, after logging in	Special software such as Tor Browser
Who can see you	Your provider and the site see your address	Same	Neither the site nor the network learns who you are, if used properly
Size	Billions of pages	Much larger than the surface web	Tiny by comparison

Most people use the deep web every day without knowing the name: anything behind a login is part of it, simply because a search engine can't and shouldn't index your inbox. There's nothing sinister about it. The dark web is a different thing: sites deliberately set up so that only anonymity software can reach them, and so that their location stays hidden.

How does Tor work?

Tor, short for "The Onion Router", grew out of research at the U.S. Naval Research Laboratory, where David Goldschlag, Michael Reed and Paul Syverson built the first onion routing prototypes in 1995 to hide who was talking to whom on a network. As the Tor Project's history records, the Tor network was first deployed in October 2002, with its code released as free software, and the nonprofit Tor Project was founded in 2006 to maintain it.

On the ordinary internet, every packet carries your IP address, so the sites you visit, and anyone watching the line, can see where traffic comes from, as how the internet works explains. Tor breaks that link. Here's how one request travels.

Walking a request through three relays

1. Pick a path. Tor Browser chooses three relays from thousands run by volunteers worldwide: an entry (or guard) relay, a middle relay and an exit relay.
2. Wrap it in layers. Your browser encrypts the request three times, like an onion: the innermost layer for the exit, then the middle, then the outermost for the entry.
3. Entry relay. It removes the outer layer and learns only the next stop, the middle relay. It knows your IP address but not where you're going.
4. Middle relay. It removes the next layer and learns only the exit. It knows neither who you are nor your destination.
5. Exit relay. It removes the last layer and sends the request to the website. It knows the destination but not who asked.

No single relay knows both who you are and what you're visiting. The cost is speed: every request makes extra hops around the world, so pages load noticeably slower. The exit relay can also see any traffic that isn't separately encrypted, which is why sites using HTTPS matter even on Tor.

What makes a site part of the dark web?

An ordinary website reached through Tor is still on the surface web; only the visitor is hidden. A dark web site is an onion service, with an address ending in ".onion", made of a long string of letters and numbers derived from the site's encryption key. It only works inside Tor.

For an onion service, the site hides too. According to the Tor Project's onion services overview, the visitor and the service each build a three-relay path, and the two halves meet at a rendezvous point in the middle: six relays in all. The traffic is encrypted from end to end, never leaves the Tor network, and the service's IP address stays protected. That is what lets a site run without anyone, including the authorities, learning where its server sits.

Onion services are a small share of what Tor carries. In July 2017, Tor co-founder Roger Dingledine said they made up only about 3% of Tor's traffic, as Wikipedia's dark web article records; most people use Tor to visit ordinary sites privately.

What's really on the dark web?

There is crime, and it is real. Markets for drugs, stolen card numbers, hacked accounts and malware have come and gone for more than a decade. Silk Road, the first well-known one, was shut down by the FBI in October 2013. AlphaBay, much larger, was taken down in July 2017 in an operation led by the United States with police in other countries; its alleged founder, a Canadian named Alexandre Cazes, was arrested in Thailand and found dead in his cell there several days later, according to Wikipedia's AlphaBay article. Stolen data from hacking attacks is often offered for sale there, and many sellers simply cheat buyers, since there's no one to complain to.

How much of the dark web is criminal has been measured, at least once. A study by Daniel Moore and Thomas Rid of King's College London, published in February 2016 from a crawl made in 2015, classified 2,723 active onion sites and found illicit material on 1,547 of them, about 57%, as Wikipedia's dark web article summarizes. That means a large minority were not, and the snapshot is now a decade old.

The legitimate uses are less visible but serious. The BBC launched an onion version of its international news site in October 2019 so readers in countries that have tried to block it, including China, Iran and Vietnam, could still reach it, as The Register reported. Facebook launched an onion address in 2014. Many news organizations use SecureDrop, an open-source system that runs as an onion service, so whistleblowers can send them documents without revealing who they are. Human rights workers, people in abusive relationships and ordinary users who don't want to be tracked use Tor for the same reason.

Still argued

Whether the benefits of anonymity networks outweigh the harms is argued among governments, police and privacy advocates. Law-enforcement agencies point to drug markets, child abuse material and ransomware gangs that hide behind them. Digital-rights groups and the Tor Project argue that the same protection shields journalists, dissidents and abuse survivors, and that criminals have other options while vulnerable people often don't. The evidence shows both kinds of use are real; how to weigh them is a judgment, not a measurement.

Is it legal or safe to use?

Using Tor is legal in most countries, including the United States and most of Europe, though some governments block or restrict it. What is illegal offline, such as buying drugs or stolen data, is just as illegal through Tor, and dark web market users have been prosecuted after takedowns.

The bigger everyday risk is being cheated or infected. Dark web sites aren't checked by anyone, fake versions of popular sites are common, and downloads can carry malware. Tor hides your location, but it doesn't protect you from a site you hand your details to, a trap the same as in phishing. It also differs from a VPN: a VPN sends your traffic through one company's server, which you must trust, while Tor spreads that trust across three independent relays.

Check yourself

• Without looking back: explain the difference between the deep web and the dark web, with an example of each.
• Why does no single Tor relay know both who you are and where you're going?
• What extra protection does an onion service give, beyond visiting an ordinary site through Tor?

Sources

• Tor Project history — The Tor Project
• Onion Services overview — The Tor Project
• Dark web — Wikipedia
• AlphaBay — Wikipedia
• BBC launches dedicated dark web mirror site — The Register, 2019
• SecureDrop — Freedom of the Press Foundation