How the speed is measured
Latency comes first: twelve small requests, timed by your browser from sending to the first byte back. Then four parallel connections download random data for eight seconds, and three upload it in 1 MB pieces for eight seconds. The first second of each is left out because connections start slowly (TCP slow start).
The result is total data over time in megabits per second. Random data cannot be compressed, so nothing along the way can make the numbers look better than they are.
Why results differ from your plan
- Wi-Fi is usually the slowest link. Test on a cable or close to the router to see your line speed.
- Distance matters: data from a server overseas arrives slower than from one nearby.
- Other devices and apps using the connection take a share.
- Plans are sold as typical evening speeds or maximums; providers publish what to expect.
Questions
- What speed do I need?
- Roughly 5 Mbps for HD video, 25 Mbps for 4K, and 3 to 5 Mbps up for a video call. A household needs the sum of what everyone does at once.
- Is this the same as my provider's test?
- No. Provider tests often run to a server inside their own network. This measures to our server across the internet, which is closer to what real websites see.