Bandwidth, data and speed are closely related terms and are sometimes used interchangeably. The amount of bandwidth that a computer connection is allotted determines how much data can be downloaded per second, or transferred from the Internet to the computer. More bandwidth equals more data per second, which translates to more speed. In some cases a bandwidth limit refers to a speed limit, and in other cases it refers to a data limit.

For example, broadband Internet services sell access plans based on speed, limiting bandwidth according to each plan. Plans with higher bandwidth limits are more expensive, but faster.

Luckily plans usually include unlimited access, so you don’t have to worry about a bandwidth limit in terms of data download. Every time you visit a webpage, after all, the page must be transferred to your computer, constituting a download. This says nothing of files, programs, videos and music you might download. Who then, has to worry about bandwidth limits?

Actually, many online services impose caps on the amount of data that can be downloaded over a set period of time. Depending on the service, data limits might apply to surfing as well as to downloading files or programs. A bandwidth limit might also apply to personal domains. Let’s take a closer look at a few examples of services that might impose a bandwidth limit.

Subscribers of mobile broadband (Internet access supplied over cellular towers), commonly apply bandwidth limits. Typically an account is allotted a large block of “free” data with charges applying for every Megabyte downloaded past the allotted amount. If the account is contractual, the allotted amount refreshes or starts over every month. If the account is pay as you go, the bandwidth limit applies to the segment of time purchased.

More commonly, we have bandwidth limits associated with domains. If you have a personal domain, the website host service likely imposes a monthly bandwidth limit on your account. Every time someone visits your website, your account racks up a download deficit that counts against your monthly allowance. The more pages visited, the more your allowance is whittled away. If you have a very low bandwidth limit and a very popular website, you might find yourself paying extra charges or having to upgrade the plan to increase the site's allotment.

Another example where you might encounter a bandwidth limit is when subscribing to a USENET newsgroup service. Services that sell access to binary newsgroups where people can share large files typically cap accounts with a bandwidth limit that prevents downloading more data from the news server than has been allotted for the month. Some newsgroup services offer plans that charge a flat monthly fee for unlimited downloads, eliminating the limit.

If you have to watch your bandwidth, consider installing a bandwidth monitor. Many of these little programs are free and will keep a running tally of downloads along with displaying real-time connection speeds. Some programs will also sound an alert at user-configurable points to announce and approaching threshold, allowing you to make better decisions about how to spend the rest of your bandwidth allotment.

If you’re only concerned about your website’s bandwidth limit, most host services feature a built-in monitor accessible through the site’s administration interface. In addition to seeing how much bandwidth your account has left for the month, the host might also provide traffic analysis, information that can help you improve site content.