What is a Download Accelerator?
A Download Accelerator also known as a Download Manager or Download Speed-up tool is an application or web browser plug-in designed to manage file downloads from websites over the HTTP protocol.
They do not speed-up your internet connection.
How do Download Accelerators work?
Have you ever tried to download a large file from a web site only to find it takes ages and if it crashes before completing then you have to start all over again?
That can be very annoying. Download accelerators work in a similar way to bit-torrent clients. They manage the downloading of a file or multiple files from a website by splitting it into several parts and download each part at the same time. They also remember where they were up to if you manually stop them or you lose your internet connection so you can resume from where you left off later.
When you connect to a web site and request a file to download, the download occurs over the single HTTP connection you made when you connected to that website. Depending on your connection to the web server hosting the website, or speed limits imposed by the web server, the download could take a very long time.
Download accelerators exploit a HTTP feature that allows you to request a part of a file. They open multiple HTTP connections to the web server each requesting a part of the same file.
Think of your single connection to the website as a straw with you sucking the download through it. With more straws tied together you can get more content faster (up to the actual limit of your internet connection) resulting in the file downloading faster.
Some web servers combat the use of download accelerators by limiting the amount of connections to any one IP address. You may have seen this if you have opened multiple browser windows to the same website resulting in one tab displaying a message such as "too many connections, try again later". This is you hitting the connection limit set by the web server.
When a connection limit is detected some download accelerators are programmed to look for mirror sites hosting a copy of the same file in order to get around any connection limits set by a single server.
Under no circumstances do they increase the speed of your internet connection.
Do I need a download accelerator?
If you have a fast bandwidth connection then a download accelerator or manager is not really necessary.
However if you make a habit of downloading very large files from web sites rather than using bit-torrent or any other P2P protocol then a download accelerator or manager may suit your needs. The files can download faster making efficient use of the bandwidth of your connection, and you will be able to resume again should a problem occur severing your connection to the website removing the need to start again.
A word of warning
Download accelerators that are free tend to contain crapware within their installers, can be embedded with ad-ware or can actually be malware in disguise, so be very wary and do your research and download only from a trusted source!
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Article date: 3rd March 2013