Testing your Internet connection's performance is a straightforward exercise. You don't need any extra software--all you need is a computer with a Web browser. But there are also a few things you can do to make sure you are getting the most accurate reading of your Internet connection. Here's what to do.
For best results, you want to use a wired connection if at all possible; that way, you don't have to worry about interference and performance fluctuations that can occur while you're on Wi-Fi. If you have any other wired devices on your home network, plug your test computer directly into the modem so those don't interfere in your testing.
If you're stuck using Wi-Fi--say, you have a MacBook Air or a tablet or some other device that doesn't have an Ethernet port--do what you can to minimize interference. Make sure your Wi-Fi router is away from other electronic devices like cordless phones, and temporarily disconnect any other devices from your Wi-Fi network--after all, you don't want another computer on your network to download a gigabyte worth of software updates while you run your tests.
While you're at it, double-check to make sure your computer isn't downloading something in the background. Check the Task Manager on Windows (summoned by pressing control-alt-delete) or Activity Monitor on OS X, and look for network statistics (it's labelled "Network"on OS X, "Networking" on Windows). Close or quit all apps on your computer to keep apps from downloading software updates while you test your connection. Your bandwidth usage may not drop to zero and stay there, but you want it as close to zero as it'll get. If your operating system is downloading updates, there isn't much you can do aside from wait and test your connection later.
If you're having any problems with your connection, now is a good idea to reset your modem and router. Switch them off and unplug them for a few moments, then plug them back in and switch them on.
Test your connection
All you have to do at this point is click the green "Begin Test" button, and Speedtest.net will check both your download and upload speed. This may take anywhere from a few seconds to a few minutes, depending on your network speed.
Speedtest.net isn't your only option for testing your connection; MegaPath (formerly Speakeasy) also offers a speed test, as well as what it calls Speed Test Plus, which tries to test the quality of your connection in addition to its raw speed. Your ISP might also offer a speed test tool, though you may need to do a little poking around for it.
If you want to track your connection's performance on a more ongoing basis, consider installing a utility like NetSpeedMonitor: This free tool for Windows XP, Vista 7, and Server 2003 lives in your taskbar, and will give you information on your connection's upload and download speeds. On OS X, the free MenuMeters utility will do much the same, though it will also track other aspects of system performance.
If your connection isn't as fast as you expect it to be, a lot of different factors could be coming into play. It could be a problem with your equipment, or it could be an issue on your ISP's end. For what to do next, see Lincoln Spector's tips on how to address a slow Internet connection. If your connection is fine but you want to tinker with it to try and get the most out of it, you can try changing your DNS server. This takes a little bit of effort, but with the right tools and a little patience, you can get a nice performance boost.