How Accurate Are Connection Speed Tests?

An internet speed test's accuracy depends on several supporting factors

A digital speedometer

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The results of an internet speed test are rarely the same because many factors affect them, some of which you can control while others not. Although an internet speed test is a good indicator of your typical speed, you shouldn't rely on it as a hyper-precise measurement.

A Speed Test Is a Simulation, Not the Reality

speed test result

Speed tests use one small file and calculate the speed by which the file both uploads and downloads from a specific test server. That test might make a good estimate of sustained bandwidth for something like a large file download or a streaming movie, but functional bandwidth accounts for network latency, name-server lookups, and related tasks.

Thus, the total amount of time required to move 10 1-megabyte files from 10 different servers is longer (often considerably so) than moving a single 10 MB file from a single server.

The Test Server Location

If you choose a server that is quite far away geographically, your test might not be that successful because your connection routes through many intermediate servers, some of which may be slower than others. 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

The more network traffic consumes your current, local, connection, the less available bandwidth you'll enjoy to perform the speed test. Thus, activity on the test computer matters, as does whether other people using your connection—like a child streaming a video on a tablet.

To get the best results, ensure that the local network and the local computer are both quiet.

Concurrent ISP Subscribers

At peak times, 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. Maybe one of the worst times to do a test is Saturday evening where most people are connected. 

This problem tends to affect people in different ways. It's less acute for most cable- and fiber-modem connections, and more acute for people using a Digital Subscriber Line connection.

Use of Proxy Servers

Many workplace computers rely on a proxy server, which monitors and controls internal networks. A proxy server with network address translation affects the speed test results, because there are some special checks and additional activity at the proxy server.