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

Fibre optic, copper, throughput speeds, ADSL and more. If you're confused by broadband terms, we can help.

Broadband is something millions of us use every day to stay in touch, work and play, using laptops, tablets and phones. Speeds available to you vary depending on many factors, including the technology and your location

What is sync speed?

Sync speed is the speed between your BT Hub and your local telephone exchange. It's sometimes called 'line rate'. Sync speed can depend on the distance from the cabinet or exchange and whether microfilters are installed correctly.

What is throughput speed?

Throughput speed is the speed at which your broadband can actually send and receive data between the internet and your BT Hub. It's what you experience at home when using your broadband connection. It can't be higher than the sync speed. It can vary throughout the day and can be slower during busy periods, especially between 8-10pm. This is the equivalent of the internet rush hour when lots of people are using the shared parts across the network at the same time.

If you run our speed tests in the Troubleshooter or My BT app, we'll show the throughput speeds to your BT Hub.

This may be different to the speed you receive on your device, which is affected by a wide range of factors. Things like the number of devices connected to your Hub at the same time and whether you're using wi-fi or a wired connection.

To see what broadband speeds you can get see Test your BT Broadband speed >

How are broadband speeds measured?

Broadband speeds are measured in megabits per second or Mbps. Each megabit is made up of 1,000,000 bits or 1,000 kilobits. The more megabits, the faster your broadband.

Faster broadband speeds means faster downloads. You can download music and movies quicker, stream from services like Netflix without waiting, and make video calls more smoothly.

The table below shows the minimum broadband speeds you need for some common activities.



Minimum broadband speed needed

Web browsing 1 Mbps (download)
HD video streaming 5 Mbps (download)
Ultra HD video streaming 30 Mbps (download)
Voice over IP 256Kbps (download and upload)
Real time online gaming 256Kbps (download) and 512Kbps (upload)
Video calling 1 Mbps (download and upload)


How do broadband speeds work?

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

Copper: 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: Faster than copper, there are two ways fibre optic broadband can get into your house.

  • Fibre to the Cabinet (FTTC) In traditional fibre, fibre optical cables run from the telephone exchange to the street cabinets. Copper cables are then used to connect the cabinet to your house. The maximum broadband speed you get depends on the distance from your house to the cabinet. The closer you are from cabinet to home, the faster your broadband. 
  • Full Fibre - sometimes called Fibre to the Premises (FTTP) or Fibre to the Home (FTTH) Here you get a dedicated fibre connection directly to your house. Your maximum broadband speed isn’t dependent on distance, so you can get the fastest speeds. FTTP provides the most reliable broadband connection.

Which BT Broadband option is right for me?

Full Fibre: Our next generation of fibre broadband gives you an ultrafast fibre optic broadband connection 25x faster than superfast fibre. Enjoy high quality video calls with friends and family, stream your favourite 4K shows on multiple devices, download HD movies and boxsets faster than ever and upload videos and high-res photos.

Fibre: Our Fibre broadband gives you a superfast fibre optic broadband connection with average speeds of 67Mbps.  Everyone in your household can get online at the same time, you can stream and download in HD on lots of devices at once and play games online.

Broadband: If you can’t get our Fibre broadband or you live in a home with lighter internet usage and fewer devices, standard Broadband is ideal for you. It’s perfect for everyday browsing, sending emails and updating your favourite social media sites.

If your broadband seems slower than usual, check out: Five steps to improve slow BT Broadband speeds.

Traffic management and fair usage policy

At busy times, internet providers can slow down traffic on the network. This is called ‘traffic management’ and it’s a way of making sure you get the best possible service. And fair usage policies are designed to stop a small number of users from monopolising the traffic at an exchange by slowing them down if they go over a certain usage cap.

We’re proud to say that our broadband packages don’t have any speed restrictions. So you don't need to worry about us slowing you down, even at peak times.

For more information, see BT's approach to broadband traffic management >

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