Broadband speed: What is it and how does it work?

Fibre optic, copper, throughput speeds, ADSL and more. Broadband is something that millions of us use every day on our laptops, tablets and phones to stay in touch, work and play.

What is headline speed?

This is the speed that you will see advertised on internet products and in adverts. There are various broadband technologies available, each capable of offering different headline speeds. Some of the common ones are:


The original broadband technology delivers speeds of up to 8Mbps


The first significant improvement delivers speeds of up to 17Mbps

VDSL (used in fibre to the cabinet)

Delivers speeds of up to 76Mbps

What is connection speed?

Your connection speed (sometimes called “sync speed”) represents the raw speed that the BT Home Hub negotiates when connecting to BT – typically from you to your local telephone exchange or from you to the cabinets, you see in the street.

What is throughput speed?

Throughput speed represents the speed at which you can actually send and receive data, and it is what you experience at home when using your broadband connection. This is also the actual speed you receive at your device when you run a speed test. This can’t be higher than the connection speed. Throughput speed is affected by a wide range of factors such as the time of day, the number of devices using your Hub at the same time, and whether you use a wired or wireless connection.

How are broadband speeds measured?

Broadband speeds are measured in megabits per second or Mb (sometimes Mbps). Each megabit is made up of 1,000,000 bits or 1,000 kilobits. The more megabits, the faster your broadband will be. Faster broadband speeds mean you can download music and movies more quickly, stream from services such as Netflix without waiting, and make video calls more smoothly.

How do broadband speeds work?

Broadband typically comes into your home via a telephone line. There are two main types of cable for doing this – copper or fibre optic – with different connection speeds.


This is used to deliver ADSL and ADSL2+ broadband from the telephone exchange to your house. The longer the length of copper, the weaker the signal strength and the slower your broadband line will have to operate.

Fibre optic broadband

Faster than copper, speedy fibre optical cables run from the telephone exchange to street cabinet. Copper cables are then used to connect the cabinet to your house. This is called ‘fibre to the cabinet’. The maximum broadband speed you get depends on the distance from your house to the cabinet, the closer you are the faster your broadband will be able to operate.

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