Do Download Accelerators Really Work?

Download Accelerators

When you click on a link in your Web browser, the browser opens one connection to the destination site and begins downloading the target file through that single connection. It's like getting water through a single hose; only so much water will arrive in a given amount of time. Download accelerators try to use multiple hoses, exploiting one of the features of the HTTP protocol.

HTTP can request specific "ranges" or segments of a file rather than the entire file. This feature lets you resume an interrupted download at the point where it was interrupted, rather than forcing you to download the entire file again. You can also pause a download deliberately and restart it where you left off.

Download accelerators open more than one connection to a Web server. Each connection requests a different range of the target file. So you have multiple parts of a file being downloaded in parallel. As the parts arrive they are assembled into the completed file. You have multiple hoses pouring water into one bucket, so the bucket fills faster… in theory. Several factors can render download accelerators ineffective.

Some Web sites are configured to limit the number of simultaneous connections they will make to a given IP address. Webmasters do this to share their limited supplies of connections and bandwidths fairly among all users. Traffic congestion between a Web server and your browser also limits the effectiveness of download accelerators. Of course, you cannot download any faster than the maximum speed of your Internet connection, either. If, for example, you're on a 5Mbps cable modem connection, a download accelerator isn't going to pull in 10 or 20 Mbps. It'll be 5 Mbps max, if you're lucky.

A few Web servers place bandwidth caps on downloading connections. In such cases, a download accelerator is actually effective because it employs multiple connections to get around the per-connection bandwidth cap. But a smart Webmaster will limit connections per IP address as well as capping bandwidth per connection.

Free Download Accelerators

Some download accelerators, such as the popular (and free) Download Accelerator Plus attempt to find mirror sites that offer the same file you are trying to download. If a mirror site is found, DAP can open connections to multiple servers. This trick skirts a single server's connection and/or bandwidth limits. But finding a mirror site is not always possible.

In my tests, I downloaded the iTunes installer file (77MB) multiple times with and without DAP, using the Firefox, IE8 and Chrome browsers. DAP didn't seem to make much difference in the download times for me, but others rave about it. If you want to try DAP, just be careful that you pay close attention during the install, to opt out of toolbars, unnecessary add-ons, and changes to your browser settings.

If you use the Firefox browser, check out DownThemAll. DownThemAll was originally created as a tool to help you download all the links or images contained in a webpage. It has evolved over the years into a fine download manager which offers acceleration of downloads, and the ability to pause and resume downloads.

One word of caution - malware is sometimes disguised as a download accelerator. Before you download and install any download accelerator, check its reputation via Google. Make sure real-time antivirus software is running on your computer before you download or install any new software. And read the fine print in the Licensing Agreement, to make sure you're not unknowingly giving the program permission to install other things without your consent.

Download accelerators do work, sometimes. But overall, they probably won't dramatically decrease the amount of time you spend waiting for large video or software files to arrive.

Do you have experience with DAP or some other download accelerator? Post your comment or question below...