Speed test Guides
Updated 23 September 2026
A gap between advertised and measured speed is normal. A huge gap is not. Here is how to tell them apart, and how to get results when the fault lies with your provider.
Plans are sold with a theoretical maximum. It assumes a perfect setup, one device connected and an uncongested network. In real life, a 10% to 30% gap on fibre is common. Measuring 80 Mbps on a 1 Gbps plan over a cable, however, points to a real problem.
Before blaming anyone, get a clean measurement:
If you cannot use a cable, say so: a complaint based on a Wi-Fi measurement will be dismissed immediately.
| Component | Common limit |
|---|---|
| Ethernet port on the computer or router | 100 Mbps on older models, 1 Gbps on most |
| Category 5 Ethernet cable | 100 Mbps |
| Wi-Fi 4 (802.11n) | often 100 to 150 Mbps in practice |
| Old hard drive | can slow a download, not the test |
On plans above 1 Gbps, the computer's network port is very often the real ceiling.
A powerline adapter, an extender, a cheap switch or an old wall socket all cut speed. Always test plugged straight into the router before blaming the line.
A plan sold as "fibre" may stop at the building and finish over copper or coaxial cable. What you measure is then that last stretch. Check your contract for the exact technology: FTTH, FTTB, FTTC, cable, VDSL.
On ADSL and VDSL, speed drops with line length. Beyond one or two kilometres, VDSL falls back to ADSL levels. Nothing on your side fixes that.
At peak times, a shared cable network or a busy mobile mast slows the whole area. Comparing your morning and evening tests makes it visible.
A badly crimped connector, a dusty optical socket, a damaged cable or failing equipment at the exchange: speed is then abnormally low around the clock, including at night.
Depending on your country and contract, a speed that stays far below what was sold may entitle you to a price reduction or to cancel without penalty. Check the rules where you live before starting a formal process.
If the cabled measurement reaches the expected speed but everything still feels slow, the problem is internal: Wi-Fi, an old device, too many connected gadgets. Our guides on slow Wi-Fi and on latency walk through the fixes.
On fibre, 10% to 30% over a cable is common, especially above 1 Gbps where the computer becomes the limiting factor. Half the advertised speed or less deserves a diagnostic.
Hardware, indoor wiring, the actual technology of the connection and sometimes even the street cabinet differ from one home to the next. Compare cabled measurements first.
It is a starting point, especially with several cabled measurements with dates and times. For a formal dispute, also use your national regulator's official measurement tool if one exists.