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High-speed Broadband

This guide will tell you what to expect from your broadband once it's up-and-running. We'll also look at what things make broadband speeds go up and down.

About high-speed broadband

You might have noticed that we refer to our broadband services as 'Up to' a certain speed. This is because high-speed broadband doesn't come as a fixed speed - it's flexible. Often, the speed you get will be automatically adjusted. This is to make sure you're getting the fastest, most stable broadband service that your phone line can support.

Ofcom's Broadband Speeds Voluntary Code of Practice

We're signed up to Ofcom's Broadband Speeds Voluntary Code of Practice which means that we're committed to providing a line speed estimate if you sign up for our broadband, or move your broadband to a new address. This is to give you an idea of the kind of speed you can expect when your broadband is up-and-running.

We'll show you a speed estimate as:

  • A single estimated speed - e.g. 6Mb (note: this is only accurate to within +/-1 Mbits)
  • An estimated speed range - e.g. 3.5 to 5Mb

Ideally your speed will be close to this estimate. If the actual speed you get is much lower than this please read and follow our Guide to Slow Speeds.

We continue to be committed to telling you about the things that can make your speed go up and down, as actual broadband speeds can sometimes be lower than estimated ones. A number of things can affect speeds and we'll tell you about them in this guide.


During the first 7 days of your broadband service

For the first week after your broadband is activated, BT keep an eye on the speed you receive. They'll run some checks to find out the lowest broadband speed you've received in the last 7 days - this is to work out what speed your phone line can support.

You'll probably see your speeds go up and down whilst this happens. You might even get disconnected now-and-again if your phone line can't handle the speed. Don't worry, this is completely normal and part of the training period.

We'd like you to help us with the tests too. So that we can get accurate results it's important that you connect to the Internet as many times as you can during the first 7 days. When you do this it's a good idea to switch the power to your modem or router off then on again (once or twice a day is fine). This will force your equipment to reconnect. After 7 days, your speeds will start to settle down and give you the best service your line can support.

After this your speed will still go up and down from time-to-time. However, the changes should be less noticeable than during the first 7 days of your service. Read on to see why this happens.


What speeds you can expect

8Mb is the theoretical maximum speed, which you'd only see under perfect conditions. So, don't be surprised if you see your broadband speed is lower than this - that's normal. If you want to see what kind of speeds you can realistically expect check out our Expected Speeds guide.


Things that can affect broadband speeds

      How this can affect your broadband speed

    Quality of the copper in your phone line

    A phone line is made up of 2 insulated copper conductors twisted round each other. Damaged, corroded copper or poor connections between cables will mean poorer speeds.

    Distance from your local telephone exchange

    A standard phone line can be several miles long, from your local exchange to your address. Shorter phone lines can support higher speeds. So, the longer the phone line the slower the speed.

    Wrongly setup microfilters

    If you've not plugged these in properly you'll not get the best broadband experience. It's a common cause of intermittent connection faults. You should avoid using long phone extension cables too. Check our Guide to Microfilters and our General Broadband Setup Guide for help.

    Traffic prioritisation

    Lots of people all making heavy downloads at the same time would could mean a poor service for other users just wanting to make VoIP phone calls or browse the web. That's why we manage our network, giving priority to different types of web traffic. Read how our Traffic Prioritisation works.

    Bad weather

    Heavy rain or thunderstorms can play havoc with broadband speeds. In fact, a severe storm could even damage your equipment permanently. We'd suggest unplugging your equipment from your phone line and power socket. You can plug them back in after the storm has passed.

    Electrical interference

    Household equipment (either yours or your neighbour's) can cause interference which often affects broadband speed. Things like TVs, alarms, fairy lights and set-top boxes are common causes.

    Age and type of your modem and computer

    Slow processing speeds and the speed of the connection between your computer and modem/router (USB is slower than Ethernet and wireless).

    Viruses and spyware

    If your computer has picked up something nasty it'll slow down your computer and connection. You should make sure you've got the latest protection installed.

Are you getting slow broadband speeds? It's worth checking the checklist above to see if any of these might be affecting you. Also, see our help with Slow Speeds.


More detailed information

Interested in finding out about the technology behind your high-speed broadband service? We've got loads of guides to choose from, just have a look at the links below. It's also worth checking out OFCOM's Code of Practice about broadband speeds

Broadband Max

Detailed information about the set of products used to provide Broadband Max. You'll also find out what lots of the technical terms relating to high-speed broadband mean. Read our article, What is Broadband Max?

General information

Find out some useful tips on dealing with slow speeds in our Broadband Speed Faults Guide.

Want to see what broadband speeds you should be getting? If we've completed a speed check for you, we show the results in your Broadband Speed section of My Account.


This page last updated 7th December 2010


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