Alongside price, speed is one of the key factors people talk about when it comes to choosing broadband.
All of the internet service providers (ISPs) quote the broadband download speed as a key part of their advertising. And then there are upload speeds, megabits and speed tests - but what does it all mean?
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Bits and bytes
Broadband speed is measured in bits per second (bps), which tells us the speed at which data is transferred. For home broadband this will be kilobits (Kbps or Kb), Megabits (Mbps or Mb) and Gigabits (Gbps or Gb).
Make sure you don't get bits confused with bytes (Kilobytes, Megabytes, Gigabytes) as these terms denote memory capacity and file size, not speed. If there's an upper case B (MB, etc) then it's bytes.
There are eight bits in a byte, so, if your download speed is eight megabits per second (8Mb), then that's actually shifting 1 megabyte per second (1MB).
It's an important distinction, because file sizes (such as songs, pictures and movie clips) are described in bytes, as are download allowances. So to recap; its bits per second (b) when talking about broadband speed, and bytes (B) when talking about file sizes and download caps.
When you connect to the internet, the download speed is the pace at which data (websites, programmes, music etc) is transferred from another source to your device.
Currently, when it comes to home broadband, advertised download speeds for nationwide providers typically range from 8Mb to 300Mb.
Pretty impressive considering that not too long ago a 2Mb download speed was seen as impressive.
However, broadband download speed doesn't have to be a big factor in your decision on which broadband deal to choose. If you're simply going to be leisurely checking your email and surfing around a few web pages, the slowest unlimited internet packages available through Broadband Genie will comfortably suffice.
That said, if you're going to be sharing the broadband between several people, downloading a lot of files (especially large ones), gaming, or listening and watching a lot of streamed content (watching the likes of BBC iPlayer, especially in HD) it will be more of a concern.
A slow internet download speed can become very annoying if your downloads take forever and the video clip you're trying to watch keeps stalling. As a general rule, if you're going to rely on downloading a lot of content, or play a lot of online games, it is definitely worth looking at getting the fastest connection you can comfortably budget for.
So what is upload speed? If you hadn't guessed, it's the speed data (such as your fab new holiday pics and videos) is sent to the internet - perhaps to put onto a social networking site such as Facebook or to a photo printing website. Essentially, the upload is going in the opposite direction to the download - from your computer to someone else's.
Broadband upload speeds are generally much slower than download speeds. The reason for this is that people generally do far more downloading than uploading, so downloading is given priority by the ISPs (who regulate how their networks deal with the various types of traffic).
Upload speeds are more important to people doing large amounts of uploading, such as someone who works from home and wants to exchange files with a remote network, or people who play a lot of online games - especially if they're hosting.
If upload broadband speeds are important to you, be sure to choose an ISP that takes its upload speed seriously. Both the Openreach (BT) fibre network (used by Sky, TalkTalk, EE and others, as well as BT) and Virgin Media's fibre offerings claim upload speeds of 10-20Mb, while ADSL is usually restricted to 512Kb, but can be 1Mb on some specialist providers.
One caveat to the above, however, is that many cheaper fibre packages come with a reduced download speed which could be far below 10Mb. So if upload speed is critical be sure to confirm this with the provider.
Dedicated business broadband can include even better upload speeds. Again, distance from your telephone exchange, as well as other considerations such as old household wiring, can also be factors in slowing down your upload speed.
For more information, read our dedicated guide to broadband and mobile broadband upload speed.
Actual speed: Why is average broadband speed important?
If you do a speedtest, please don't take it as gospel - and don't think doing several in a row gives you an accurate result either. If you really want to know your average broadband speed you'll need to do a series of tests at different times, as well as on weekdays and weekends.
Most broadband services are on 'contended' lines, which means many users in different homes/businesses can be using the same line at the same time. This can potentially slow your internet usage at peak times - especially if a particular provider favours certain types of internet traffic over others (perhaps video streaming over peer-to-peer file sharing).
And there are many other reasons why you won't always get your advertised speed - in fact it's likely you'll never reach 17Mb on an 17Mb line, even if you can see your telephone exchange out of your window. While advertised download speeds tend to start at around 8Mb, this can cover a big range - one person's 8Mb connection can average anything from 1-8Mb or slower.
The reasons for this are twofold. First, not all ADSL telephone exchanges are built equal: some still have older technology capable of a top speed of 8Mb, while improved ADSL2+ exchanges can hit 17Mb. But these all rely on copper wires, which lose data over distance (which has to be re-sent) - hence distance from the exchange being important.
However, as fibre cable becomes more common place as data 'drops' are much less of a problem with fibre cables, which are perfect for transferring data (remember, those old copper networks were designed for voice calls).
The actual download speed you will achieve is dependent on a number of factors too though. ISPs will now tell you during the sign-up process what maximum speed you are likely to get - if they don't, make sure to get them to check. People living in big urban areas are likely to have access to faster speeds that those living in the countryside. Even then though, factors such as internal wiring and Wi-Fi can further slow your speed.
How fast is my broadband connection?
So how can you find out the actual download speed and upload speed? The easiest way is to do a broadband speed test, and Broadband Genie offers one of the best and most reliable ones around: just head over to our speed test and follow the simple instructions - it's fast and free. We also have a separate mobile broadband speed test for smartphones, tablets and dongles.
There are a couple of things to note with a broadband speed test: before you do a test, make sure you have closed any other applications using the internet such as email and instant messaging programs. Secondly, your broadband speed can vary wildly at different times of the day depending on external factors, such as the number of users online in your building, your street, and even your country. Also, as more people are online, some ISPs deliberately slow down lines in busy periods of the day - this is called 'traffic shaping'.
For these reasons, make sure you do a number of broadband speed tests at different times of the day - and on different days (weekdays, weekends etc) - to get a better picture of the kind of broadband speeds you are receiving.