Testing the width of the pipe
Throughput is the amount of data that can be transferred over your Internet connection at one point in time. There are a number of free sites which allow you to check thus the current throughput you can get on your Internet connection. Factors such as network congestion and other downloads in progress can affect the available throughput.
Please be aware that ZDNet's Broadband Speed Test measures the data throughput between a computer and a geographic distributed network of servers to calculate how fast broadband speeds are in the real world. The results are not an indication of the actual line speed between the user and the ISP. There are many external factors such as network congestion and routing between multiple networks that can affect individual results, which means the broadband speed test does not necessarily warrant 100% accuracy.