Speedtest.net is a free tool that measures the performance of your internet connection.
The online app uses a large international network of servers to simulate the uploading and downloading of files. Click on the Begin test button on Speedtest.net and you'll be invited to run the test using either the default server, or choosing one yourself from the map. Speedtest.net will then perform a latency test, before measuring download and upload performance.
Your results are displayed in a small, easy-to-understand window, which you can copy to your desktop if you like. This shows you the download, upload and ping speeds, along with information about your ISP and the server that was used in the test.
There's plenty of extra analysis available on Speedtest.net if you want it. The service can show how your result compares with your ISP's average, and the Your Results section gives a more detailed breakdown of the test process, which can be exported as a CSV file.
If you're geeky about internet speeds then it's well worth having a look at Speedtest.net's World Results section, where you can check out stats about internet performance in countries and cities around the world.
On the downside, Speedtest.net doesn't allow you to set individual package sizes to analyze and the test isn't very configurable in general.
Speedtest.net represents an easy and clear way to measure your internet speed, although the validity of the results cannot be assured.