How Does the Internet Work? Packets, Cables and the Journey of a Web Page

You type an address, press enter and, within a blink, a page full of text, images and video appears. It feels like magic, or like the information was already sitting in your device. In reality, in that fraction of a second, data has been requested, broken into pieces, sent through dozens of machines, perhaps across an ocean, and reassembled on your screen. Here is how it works.

A network of networks

The internet is not one big computer or one company. It is a global network of networks: home networks, mobile networks, company and university networks, all connected together. According to the International Telecommunication Union (ITU), around 5.5 billion people, roughly two-thirds of humanity, used the internet in 2024.

What makes this possible is not a single cable but a set of shared rules, called protocols. As long as every device speaks the same protocols, it can exchange data with any other, no matter who made it or where it is.

The most important of these, TCP/IP, goes back to a 1974 paper by Vint Cerf and Bob Kahn, which described how separate networks could be linked into one. In 1983, the ARPANET, a US research network, switched over to TCP/IP, a date often called the internet’s birthday.

The journey of a web page

1. Finding the address: DNS

Computers do not find each other by names like “factwonder.com” but by numbers called IP addresses. So the first step is a lookup in the Domain Name System (DNS), often described as the internet’s phone book. Your device asks a DNS server, “What is the address of this site?” and gets back a number. The answer is often stored nearby, so it arrives in milliseconds.

2. Breaking data into packets

The server does not send the page as one giant block. It breaks it into thousands of small packets. Each packet carries a piece of the data plus a label: the destination address, the sender’s address and a sequence number. This idea, packet switching, is what makes the internet so robust: if one path is blocked, packets can simply take another.

3. Hopping between routers

Packets travel through routers, specialised computers that sit where networks meet. Each router looks at a packet’s destination and sends it one step closer, along the best path it knows. A typical packet passes through perhaps 10 to 20 routers. Packets from the same page may even take different routes and arrive out of order.

4. Putting it back together

On your device, the TCP protocol collects the packets, puts them back in the right order and asks for any lost ones to be sent again. Only then does your browser receive the complete page, read its code and draw it on the screen. Images, fonts and videos each go through the same process, often all at once.

The layers of the internet

Engineers think of the internet in layers, each with its own job:

This layered design is why the internet could grow so much. A new app does not need new cables, and a faster cable does not require rewriting every app.

Cables under the sea

We talk about “the cloud”, but the internet is very physical. Data between continents travels mainly through submarine fibre-optic cables lying on the sea floor, a network of several hundred cables that can be explored on TeleGeography’s Submarine Cable Map. Over 95% of intercontinental traffic goes this way, because cables carry far more data, more cheaply and with less delay, than satellites.

Inside a fibre-optic cable, data travels as pulses of light through glass strands thinner than a hair, at about 200,000 km per second. A message from Europe to America can cross the Atlantic in under 40 milliseconds. Cables are occasionally damaged by ship anchors or earthquakes, and specialised ships are sent to repair them.

On land, the data then flows through national backbone networks, data centres full of servers, and finally the cable, fibre or mobile link to your home or phone.

The internet and the web are not the same

People often use the words interchangeably, but the World Wide Web, invented by Tim Berners-Lee at CERN in 1989, is just one service that runs on top of the internet. Email, video calls, online games, music streaming and messaging apps all use the internet too. Today most websites use HTTPS, which encrypts the data so that routers along the way cannot read it.

In short

• The internet is a network of networks joined by shared rules called protocols.
• DNS turns a site name into a numeric IP address.
• Data is split into packets that routers pass along, step by step.
• TCP puts packets back in order and re-requests missing ones.
• Most intercontinental data travels through undersea fibre-optic cables, not satellites.
• The web is only one service running on the internet.