How the Internet Works<br>English

How the Internet Works<br>No technology has transformed daily life as much since the 1990s.

The share of the population with Internet access doubled between 2014 and 2025, reaching 73.2% of the world population in October 2025.<br>The Internet is a network used by more than 6 billion people, but how it works is still opaque to many.

The Internet is the network that connects devices to each other. The web (World Wide Web) is only one of the services that run on the Internet, alongside email (SMTP) or file transfer (FTP).

The web is a collection of pages accessible with a URL that starts with HTTP. This abbreviation refers to a protocol (HyperText Transfer Protocol) that standardizes how computers communicate on the web.

In this article, we will mainly use the web as an example to illustrate how the Internet works.

Accessing the Internet

Devices have three ways to access the Internet (Wi-Fi, Ethernet, 4G/5G). The process is slightly different for each method.

Wi-Fi

From a fixed location, accessing the Internet requires a home router (an Internet box). A box typically contains:

The modem . It converts digital data from the device into radio waves to send to the server.

The router . It manages traffic and directs data between devices by assigning IP addresses and handling routing.

Each Wi-Fi-capable device has a Wi-Fi card. This card receives the radio waves emitted by the box.

The card and the box are transmitters/receivers configured on the same frequencies (2.4 GHz or 5 GHz). To receive signals from other devices, a device must be on the same frequency to exchange information.

Frequency measures how many repetitions per second a wave has. It is measured in Hertz . For the Internet, these are considered low frequencies. The higher the frequency, the shorter the range. For example, 5 GHz Wi-Fi is faster but has a smaller coverage area.

Going further: beacons

Routers emit beacons by radio waves. Every 0.1 seconds, a beacon is sent to Wi-Fi cards to detect the network.

This almost permanent connection allows the device to measure the strength of the received beacon, which displays the signal quality with connection bars.

Each device has a maximum number of megabits per second it can handle, which allows the router to adapt to different device generations.

Beacons are encoded in binary (content made of 0s and 1s. For example, the letter A in binary is 01000001).<br>They are transmitted as radio waves. To transmit binary information, the components of the wave are modified.

The 0s and 1s become easily distinguishable, which allows the device to properly decode the received information.

5G

Without access to a Wi-Fi network, mobile data takes over and keeps you connected to the Internet.

Each phone has a modem, which enables both calls and mobile data. Not all modems are compatible with 5G by default. 5G uses new frequencies, especially to handle increased traffic. 4G modems cannot process these new frequencies.

The modem detects nearby 5G cell towers. Each tower continuously broadcasts a "beacon signal" that contains identification information: the operator, the network type (5G, 4G, 3G), signal strength, etc.

The SIM card provides authentication and allows the device to use authorized operators. Even if several towers are available, the modem chooses the best one.

The range of cell towers depends on the frequency used. With low frequencies (700 MHz), towers can work up to 15 km in rural areas, compared to 3 km in cities because of obstacles. The higher the frequency, the shorter the range. Mid-band 5G towers have a range of 400 m to 1.2 km.

Unlike Wi-Fi, the IP address is public in 5G. Now that the device is connected to the Internet via Wi-Fi or 5G, let's see how the network operates.

IP address

The Internet relies on IP addresses. Like a physical address, it tells where to send and receive information.

A Wi-Fi network gives access to several devices and assigns a private IP address to each device.

Online, requests come from a public IP address, which is the router's address. The server never knows which device made the request thanks to NAT . NAT (Network Address Translation) transforms a public IP address into a private IP address and vice versa.

To better understand NAT, it helps to distinguish three types of addresses:

Public addresses visible on the Internet

Private addresses used in the local network. Inside the router, a DHCP (Dynamic Host Configuration Protocol) server assigns this private address.

Local addresses internal to a machine (127.0.0.1)

When a computer sends a packet to Wikipedia:

The packet leaves with source IP: 192.168.1.42.

The router intercepts it and replaces it with a public IP: 192.168.1.42 -> 86.210.x.x (its public IP). It also assigns a unique port (e.g., 12001).

The router keeps a record: "192.168.1.42 made this request on port 12001".

Wikipedia responds to port 12001.

The router forwards it to the source IP...