Most of you have probably heard that the amount of bandwidth usage or data transfer allocated with a hosting plan is an important aspect to consider, but what exactly is it?

To begin let's clarify a common misconception. Many people, some hosting companies included, incorrectly use the terms bandwidth and data transfer interchangeably. While similar, these are actually two different things.

The term bandwidth refers to how much data can be moved at one time from a web server out onto a network and across the Internet. You can think of bandwidth as the diameter of a water pipe. The bigger the diameter of the pipe, the more water you can move, even if the water is moving at the same speed.

Data transfer (AKA bandwidth usage) refers to how much data/information is sent to or received from your hosting account on the server over a specified period of time. In most cases data transfer is measured monthly, although it can be measured daily in high volume situations. Looking back to the analogy we used before, data transfer would be the measure of how much water has actually flowed through our pipe over a given period of time.

Every time someone views your web page all of the data (html code, text, graphics, etc.) incorporated within the page must be transferred from the web server, across the Internet, and onto the visitor's computer where it is viewed via a web browser. As a result, the amount of data transfer a hosting customer uses is directly related to the number of visitors to their site, multiplied by the size of their web pages, including any graphics displayed within.

In most cases it is these graphics and other multimedia files which account for the vast majority of data transfer used. This becomes apparent when you consider that the average text page consists of only of about 5 Kb of data, while images can be as large as 50-200 Kb in size -- and many images are often incorporated into each web page.

Macromedia flash files are often very large, along with audio and video files. Live audio and video feeds can also be incredibly bandwidth intensive.

It is important to note that bandwidth also includes e-mail and FTP transfers towards your monthly data transfer totals. As a result, if you plan on maintaining a mailing list or allowing your visitors to download large files via FTP (such as graphics or software) you should plan accordingly when attempting to judge your monthly level of data transfer.