Broadband speed is one of the biggest concerns to anyone thinking about changing their broadband connection, and rightly so. After all, it's the speed that we probably notice most of all about a broadband connection, and it's the speed that effects exactly what we can do online. Slower broadband, for example, makes watching HD content online impossible, while fast broadband can make it very easy to stream HD services or download huge files in minutes rather than hours. Speed is even more important when you live with others and need to make sure that everyone in your house can access the internet at a good rate.

The problem with broadband speed is that it's not always that easy to tell what you're going to end up with when you are out looking for a provider online. A lot of providers advertise their speeds as 'up to' a certain amount, but it's important to remember that it's unlikely you'll see the upper limits of that amount due to the way most broadband works.

The vast majority of broadband providers in the UK use a technology called ADSL. There's a lot of tech stuff involved, but all you really need to know about ADSL is that it delivers broadband through your phone line. The broadband signal is split from your local telephone exchange, sent down a copper cable into your home where your router and computer sort out the data. This system is popular because nearly everyone in the UK has access to a phone line, providing coverage of about 98% overall. It's also cheaper, as there's no digging or extra installation work to be done because in most cases a phone line will already exist to a property.

The problem with this technology is that it's really old. Copper cables were never designed to carry internet data on them so the signal degrades the further it has to travel. This means that if you live 3 miles away from your local exchange, your broadband speeds will be very slow, while if you live next door to your exchange, you should be able to get very fast speeds. Essentially, broadband speed through ADSL is far more to do with where your actual house is in relation to the telephone exchange than any choice you can make about different providers.

Of course, not everyone knows their exact distance from their exchange, which is where online speed checkers can come in handy. Not to be confused with the other type of speed test which tests your current connection speeds, a broadband speed test can be used to test the potential speed of a connection you haven't signed up to yet. The test works out how far you are aware from your exchange and what different technologies your exchange has available and then uses this information to guess your potential broadband speed.

This can be done be entering either your postcode or telephone number into the test, although telephone number tests are usually a little more accurate. No test is completely 100% correct, but it's a pretty good indicator of what speed you'll actually get. Having this in advance is very useful, as it means you already know the limits of your connection and can adjust your choices accordingly. For example, if your maximum broadband speed is around 6 Mbps, then there's not much point paying extra for an up to 24 Mbps package.