Although online Internet speed tests vary in the technologies used to approximate real-world testing conditions, most involve opening a browser, navigating to the speed test website and clicking on a button to start the test. SpeedOf.Me and SpeedTest.Net both offer free online speed tests.
Although there are many online speed tests available, there is no agreement about the extent to which the tests' underlying technologies affect the results. The most common technologies employed are HTML5, Java or Flash. Methods within speed tests differ as well; some download and upload single large files, while others work with files of differing sizes loaded serially or in parallel.
Reviews of online speed tests often report up to tenfold differences in resulting download or upload speeds. Besides differences in the speed tests, many other factors affect the outcome of the tests. The number of test servers and their geographic proximity affect latency. Load on the server and on the client and the amount of other traffic along the path can dramatically affect the results. All in all, the closer to the client a server is, the fewer hops for connection. Using a testing service closer to home reduces the latency and the possible paths from server to client, increasing the consistency among tests.