Question: How Accurate Are Speed Tests?
No speed test engine can give 100% accurate results, because there are factors on which the results depend, some of which are out of control. While most tests online somewhat stray from what we can call accurate, a few are quite worthy, with sophisticated algorithms and reliable results.
Answer: The results of a speed test are rarely the same all the time. This is because there are a number of factors that affect them, some of which you can control while others not. The factors that affect the accuracy of a speed test are:
A speed test is a simulation, not the reality
What is the reality like? Whether it is browsing, whereby small HTML files are downloaded each time you click on a link, or phoning, whereby voice packets are sent to and from your machine, the traffic activity is quite different from that of a speed test, which involves downloading a sample file. In consequence, the result obtained is not exactly what you experience when you use your connection.
The test server location
If you choose a server that is quite far away geographically, your test might not be that successful. Choose one in your area (continent, ocean). Some tests suggest a suitable list of servers from which you can choose one.
Concurrent Internet activity on your connection
If you have another application consuming bandwidth (like a file downloading), it will affect the test results.
Concurrent ISP subscribers
At peak time, there is very often a drop in quality of connection with most ISPs. This is because many people are connected to the Internet through the ISP at that time. This will affect speed test results as well.
The use of proxy servers
If you are using, say, your corporate network at your place of work, there is a big chance that you are behind a proxy server. This, with NAT (network address translation), can affect the speed test results, because there are some special checks and additional activity at the proxy server.
Simultaneous tests being run on the same server
Obviously, the more there are speed tests being done on one server, the more jammed the connection to it is. As a result, test results will be affected.