Latency is the time it takes a packet of data to travel from its source to its destination. Low latency means few delays, and high latency means many. A rule of thumb for internet delay is to multiply the straight-line distance by 2.1 and divide by the speed of light in fiber.

The first request to a website takes longer because it includes a DNS lookup, a TCP handshake and the secure TLS negotiation, while later requests reuse the connection. On a secure web page the steps come in a set order: first a DNS lookup, then the TCP handshake, then the TLS handshake. TLS needs a reliable, in-order connection underneath it, which is why it starts only after TCP has set one up.

A web page needs many requests for its HTML, style files, scripts and media, so the more and bigger the requests, the more a slow connection is noticed.

A content delivery network is a group of servers spread out over many places. The servers keep copies of data and answer each request from the server closest to the person asking, which can make a site faster, because a nearer server means a shorter trip for the data. Using a content delivery network has a price, because a website now depends on another service, and if it goes down or is blocked in a region, the website can stop working.

An IPv4 address is 32 bits long, which allows about 4 billion addresses. On 3 February 2011 the central pool handed out its last blocks to the five regional registries. The regional registries ran low at different times, and the Asia-Pacific registry, APNIC, was first to reach its final block, on 15 April 2011, while Europe's registry, RIPE NCC, made its final regular allocation on 25 November 2019 and said it had run out of IPv4 addresses. IPv6 was made to fix the shortage: it raises the address size from 32 bits to 128 bits.

Big networks on the internet are called autonomous systems. Each one is a set of routers under a single technical administration. Neighbouring networks use the Border Gateway Protocol, BGP, to swap network reachability information. Routers share information about which networks they can reach using BGP, which is how networks learn paths to each other.

Browsers come with a built-in list of trusted root certificates, and they check that a site's certificate was signed by a certificate authority that chains back to one of them. A website's digital certificate ties its domain name to its keys, so the browser knows it is really connected to that site.

Major browsers began removing support for the old TLS 1.0 and 1.1 versions in early 2020. As of November 2026, servers should use TLS 1.2 or 1.3.

Tim Berners-Lee wrote a program called Enquire in 1980 while consulting for CERN, which let him link any pieces of information to each other. In September 1990, his boss at CERN agreed to buy a NeXT computer so he could write a global hypertext system. On 12 December 1991 Paul Kunz installed the first web server outside Europe, at the Stanford Linear Accelerator Center in California.

Repair crews use tools such as a cut-and-hold grapnel, which cuts a cable and grips it on one side of the cut. As of early 2025, a repair itself takes about one to two days, mostly for splicing the glass fibers, not counting the ship's trip to the site. But ITU says repair delays can last weeks or months, and one expert says some countries take an average of six weeks to approve a repair.

A typical user in a high-income country generated nearly eight times more mobile data than one in a low-income country, in ITU's 2025 estimates. In ITU's 2025 data, 94 percent of people in high-income countries used the internet, compared with 23 percent in low-income countries.

As of November 2026, almost all the data that travels between countries goes through cables laid on the sea floor. Light travels through glass fiber at about 204,500 kilometers per second, only about 68 percent of its speed in a vacuum, where light takes 3.33 microseconds to cover a kilometer, whereas fiber delays a signal by about 5 microseconds for every kilometer of path.

Words to know

• latency: travel delay
• vacuum: empty space
• autonomous: self-governing
• registries: address managers
• grapnel: hook-like tool