Speedtest by Ookla, Fast.com, Google, nPerf: which speed test should you use?
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You run Speedtest by Ookla, then Google's test, then ours, and get three different numbers. None is "wrong": each tool measures a different path across the internet. Here is how they work and how to choose.
What a speed test measures
A speed test sends and receives data between your device and a measurement server, then calculates the speed. The result depends on three things:
- your connection (fibre, ADSL, 4G, Wi-Fi or cable);
- the server, its distance and capacity;
- the method: number of parallel connections, test length, average or median.
The main tools
| Tool | Servers used | Characteristic |
|---|---|---|
| Speedtest by Ookla | Large server network, many hosted by providers | Several parallel connections, idle and loaded latency |
| Fast.com | Netflix servers | Shows download first; upload and latency under "more info" |
| Google's test | M-Lab measurement platform | Launched from Google Search, shows the server city |
| nPerf | nPerf server network | Also offers mobile coverage maps |
| Cloudflare | Cloudflare network, hundreds of cities | Measures loaded latency and packet loss |
| SpeedFibre | Closest Cloudflare server | Sustained speed, latency under load, plain-English verdicts |
Real example: a 200 Mbps fibre line
On the same fibre line, over Wi-Fi, a few minutes apart:
| Tool | Download | Upload | Ping |
|---|---|---|---|
| Speedtest by Ookla | 202.9 Mbps | not recorded | 28 ms |
| Google's test (server in Lisbon) | 217.9 Mbps | 179.7 Mbps | 44 ms |
| SpeedFibre | 196 Mbps | 189 Mbps | 27 ms |
All three confirm the same reality: about 200 Mbps, in line with the plan. The gaps come from the servers (a server in another country versus one in the same city, for ping) and the calculation methods.
Why a test can read too high or too low
- Too high: some networks let a burst of speed through in the first fractions of a second. A very short test measures that burst instead of real speed. That is why our test calculates speed over transfers lasting several seconds.
- Too low: distant or busy server, weak Wi-Fi, another device downloading, an old phone.
- Different ping: it depends directly on distance to the server. A server in your own city gives a lower ping than one abroad.
Measure your connection now. Start the test
Getting a reliable measurement with any tool
- Connect a computer over an Ethernet cable.
- Close other apps and pause other devices.
- Run 3 tests and keep the middle value.
- Test at different times of day, especially in the evening.
- To compare two tools, run them one after the other, in the same place.
Which tool should you choose?
To check your plan, any serious tool will do, provided you follow the method above. For a diagnosis, what matters is what comes after the number: knowing whether the problem is Wi-Fi, the line or the network. That is what our guides are for, such as slow internet: causes and fixes and how to read a speed test.
Sources and further reading
Frequently asked questions
Which speed test is the most accurate?
There is no single one. Serious tools give close results if you test over a cable at the same time. Gaps of 5 to 10% are normal.
Why does Fast.com show a different result from Ookla?
Fast.com measures downloads from Netflix servers, while Ookla uses other servers, often at providers. The network path is not the same.
Why does ping change from one test to another?
Ping depends mainly on distance to the server. A server in your own country gives lower ping than one on another continent.
Is SpeedFibre linked to Ookla?
No. SpeedFibre is an independent tool. Speedtest is a trademark of Ookla, mentioned here for comparison.
The SpeedFibre team Guides written and reviewed by a telecom engineer specialised in fibre optics (FTTH), with more than 8 years of hands-on network maintenance and measurement. Editorial policy.
Related guides
- Understanding your connectionHow to read a speed test: download, upload, ping and jitter
Download, upload, ping, jitter: learn what each value of a speed test means, what a good result looks like and how to find the cause of a slow connection.
- Understanding your connectionPing, latency and jitter explained simply
What are ping, latency and jitter? Normal values on fibre, ADSL and 4G, their impact on gaming and video calls, and how to improve them.
- TroubleshootingFibre slow on Wi-Fi but fast on cable: why, and how to fix it
Your fibre reaches full speed over Ethernet but not over Wi-Fi? The real limits of Wi-Fi, normal speeds by device and 8 practical fixes.
- Understanding your connectionMbps vs MB/s: the difference between megabits and megabytes
Why does a 100 Mbps fibre download at 12 MB/s? Understand megabits vs megabytes and work out how long a file will take to download.
