How does the internet work? A plain-words guide

The internet is a global network of networks: tens of thousands of separately run networks that agree to pass each other's data using shared rules called TCP/IP. How does the internet work? It breaks everything you send, a message, a photo or a web page, into small packets, labels each with the address of the computer it's going to, and hands it from router to router, often through undersea cables, until it arrives and is put back together.

In short

• Data travels in packets, each carrying a destination address, and each can take its own route.
• The Domain Name System turns names like example.com into the numeric addresses routers actually use.
• No single body owns or runs the internet; independent networks connect by agreement and follow open standards.

What happens when you open a website?

The clearest way to see how the internet works is to follow one request. Say you are in London and type the address of a site whose server sits in New York.

1. Your device to your router. Your laptop sends the request over Wi-Fi, as radio waves, to the router in your home. The router connects your home network to the outside world.

2. Your router to your provider. The router passes the request over a cable, fiber or phone line to your internet service provider (ISP), the company you pay for access. The ISP's network is one of the many networks that make up the internet.

3. A name becomes a number. Computers on the internet find each other by numeric IP addresses, such as 203.0.113.7, not by names. So before anything else, your device asks the Domain Name System (DNS), a worldwide directory, for the address of the name you typed. Usually a nearby DNS server already knows it. If not, it asks up a chain: one of the root servers points to the servers for ".com", which point to the servers for that one domain, which give the answer.

4. Packets cross the networks. Your device opens a connection to that address and sends the request as packets. Routers, specialized computers at every junction, read each packet's destination and send it one step closer, much as a sorting office forwards letters. The packets leave your ISP, cross into other networks at exchange points where networks meet, and travel under the Atlantic through a submarine cable. Across most of the ocean such a cable is about as wide as a garden hose, and its glass fibers, each about as thin as a hair, carry data as pulses of light, according to TeleGeography, which tracks them.

5. The server answers. The server in New York receives the packets, works out what was asked for, and sends back the page, the images and the code, again as packets. Your browser reassembles them and draws the page.

How long does that take? A worked example

London to New York is about 5,600 km in a straight line, and more along the cable's actual route. Light in glass fiber travels at about two-thirds of its speed in a vacuum, roughly 200,000 km per second. One way, that's at least 5,600 ÷ 200,000 = 0.028 s, or 28 milliseconds. A round trip, there and back, is at least 56 ms; in practice, with a longer route and time spent in routers, it's closer to 70 or 80 ms.

A secure web page needs several round trips to the server before the first byte of the page arrives: one to set up the connection (TCP), one to agree on encryption (TLS, the padlock in your browser; the current version, TLS 1.3, needs one round trip where older versions needed two), and one to ask for the page and get the start of the answer. Three round trips of 75 ms is 225 ms, about a quarter of a second, plus the time to look up the name if it isn't already known nearby. Newer protocols such as QUIC, used by HTTP/3, fold the connection and encryption steps together to save a round trip, but none can beat the distance. Distance, not just bandwidth, sets a floor on how fast the internet can feel. That's why large sites keep copies of their pages in data centers close to their users, a big part of what cloud computing provides.

The page itself might be 2 MB. Data on most networks moves in packets of at most about 1,500 bytes, so that page arrives as roughly 1,400 packets, each finding its own way and all of them put back in order at your end.

What do TCP and IP actually do?

The internet's rules are layered, each layer doing one job and trusting the others to do theirs.

Layer	Job	Examples
Link	Move bits across one physical hop	Wi-Fi, Ethernet, fiber, 5G
Internet	Address packets and route them between networks	IP (IPv4 and IPv6)
Transport	Make a reliable conversation out of unreliable packets	TCP; UDP for speed over reliability
Application	Do something useful	HTTP for the web, SMTP for email, DNS

IP, the Internet Protocol, gives every packet a source and destination address and makes a best effort to deliver it, with no promises: packets can be lost, duplicated or arrive out of order. TCP, the Transmission Control Protocol, sits on top. It numbers the packets, has the receiver confirm what arrived, resends what didn't, and puts everything back in order. Together they turn a messy, shared network into what looks like a clean connection between two computers.

That split is the internet's central design choice. The network in the middle stays simple and just forwards packets; the intelligence lives at the edges, in the computers at each end. It means a new application, from email to video calls, can be invented without asking anyone to change the network.

Where did the internet come from?

The internet grew out of ARPANET, a network funded by the U.S. Defense Department's research agency. As the Internet Society's history, written by several of its builders, records, the first node was installed at UCLA in September 1969 and the first host-to-host message went from Leonard Kleinrock's lab to the Stanford Research Institute a month later. The idea of packet switching came from Kleinrock, Paul Baran at RAND and Donald Davies at Britain's National Physical Laboratory in the 1960s.

In 1973 Robert Kahn and Vint Cerf began designing TCP/IP so that different networks could join into one. On 1 January 1983, ARPANET switched over to TCP/IP all at once, a date often called the internet's birthday. The World Wide Web came later, in 1989–91, as one service running on top of the internet.

Who runs the internet?

Nobody and everybody. No company or government owns it. Each network, whether a home ISP, a university, a mobile carrier or a cloud company, runs its own equipment and agrees with others to exchange traffic, sometimes for a fee and sometimes for free.

A few bodies coordinate what must be shared. The Internet Engineering Task Force, an open community of engineers, develops and maintains many of the internet's core technical standards, including TCP/IP. ICANN, a nonprofit, coordinates the global systems of domain names and IP addresses. The DNS root, the top of the naming system, rests on 13 named root server authorities, lettered A to M, operated by 12 organizations including universities, companies, U.S. government agencies and nonprofits, each with many copies around the world. Governments regulate the networks in their own countries, and some filter or shut them down, but none controls the whole.

The internet's reach keeps growing. The International Telecommunication Union estimated in November 2025 that about 6 billion people, roughly three-quarters of the world, were using the internet that year, while 2.2 billion remained offline.

Is the internet the same as the web?

No. The internet is the network of connections; the web is the collection of linked pages you reach with a browser, and it is only one of the things the internet carries, alongside email, video calls, online games and app traffic. Search engines index the web, not the whole internet. The difference is worth its own note: the internet vs the World Wide Web.

Check yourself

• Without looking back: follow one web request from your laptop to a server abroad and back, naming each step.
• What problem does DNS solve, and what would you have to type without it?
• Why does TCP exist if IP already delivers packets?

Sources

• Brief History of the Internet — Leiner, Cerf, Clark, Kahn, Kleinrock and others, Internet Society, 1997
• Submarine Cable Frequently Asked Questions — TeleGeography, 2026
• Root Servers — Internet Assigned Numbers Authority
• Introduction to the IETF — Internet Engineering Task Force
• Facts and Figures 2025 shows steady progress in connectivity, while highlighting gaps in quality and affordability — International Telecommunication Union, 2025