On mobile data, one test uses 10 to 60 MB depending on the connection speed (download and upload included), and much more on a very fast connection.

How the test works

The test exchanges files with the Cloudflare server closest to you and times each exchange. It has three stages:

Latency: the browser sends 20 empty requests, after a first one that opens the connection, and measures the round trip of each. The latency shown is the median. Jitter is the average difference between two consecutive measurements: the lower it is, the more stable the connection.
Download: the browser receives larger and larger files (100 KB, 1 MB, 10 MB, 25 MB and 100 MB). It moves to the next size as long as a file arrives in under a second. The speed of each file is its size divided by its transfer time.
Upload: the same principle in the other direction, with files sent to the server. The latency measured in the first stage is subtracted from each duration.

The result kept is the 90th percentile of the measurements, as in Cloudflare's own test: the slowest measurements, slowed down by the connection start-up, are left out. Small files only warm up the connection; only transfers long enough to be reliable count. The test stops after about ten seconds per stage to limit data use.

Fibre, 4G and 5G: what speed to expect

The speed this test measures depends first on the technology that reaches your home or your phone. Fibre to the home, a 4G or 5G router and a satellite link behave very differently, both in speed and in latency. Knowing your technology tells you whether your result is normal or whether something is wrong.

Fibre to the home (FTTH)

Fibre carries the signal as light all the way to your home. It is the fastest and most stable fixed technology: speed hardly drops with distance and upload is usually much higher than on older lines, sometimes equal to download. Latency is low, which shows in video calls and online games. If you have fibre and a wired test gives much less than your plan, the problem is most often the router, the in-home wiring or the device you test with.

4G LTE and home 4G routers

On 4G, speed depends on the signal, the distance to the mast, walls and the number of people using the same mast. The same phone can give very different results indoors, in the street or in a crowded mall. Home internet routers with a SIM card work the same way: placing the router near a window often improves the result.

5G and home 5G routers

5G offers more capacity and lower latency than 4G, but only if your device supports it, your plan includes it and you are inside a 5G coverage area. Outside it, your device falls back to 4G without making it obvious. If the test gives a 4G-like result, check the network icon in your phone's status bar or the router's interface.

Satellite internet

Satellite links serve remote areas without fibre or good mobile coverage. Speed can be good, but latency is higher because of the distance the signal travels: with geostationary satellites, about 36,000 km up, it shows in calls and games. Low-orbit systems reduce this delay. Obstacles in front of the dish and heavy weather also affect the service.

What each figure means

Download: how fast you receive data. It matters for streaming and downloading files.
Upload: how fast you send data. It matters for video calls, online classes and cloud backups.
Latency (ping): the round-trip time of a packet, in milliseconds. The lower, the more responsive games and calls feel.
Jitter: how much latency varies. When it is high, voice breaks up even if speed is good.

Is your speed lower than your plan?

Before complaining, rule out causes on your side. You will then have clear evidence if you need to file a complaint.

Test over a cable. Connect a computer to the router with a network cable and close downloads, updates and other tabs. Wi-Fi loses speed with distance, walls and neighbouring networks.
Repeat the test at different times. Test in the morning, afternoon and evening over several days. Note the date, time and results, or take screenshots.
Restart the router. Unplug it for a few seconds, plug it back in and wait for the lights to settle. Also check the cables are properly connected.
Check your device. An old computer or phone, or a slow network card, can cap the result even when the line is fine.
Complain to your provider first. Open a complaint with your provider's customer service, with your measurements, and keep the ticket number.
Escalate to the CST if needed. If the provider does not resolve the complaint within 5 days, or closes it without dealing with it, you can escalate it to the Communications, Space and Technology Commission (CST) within 180 days, through its Telecom Complaints Escalation service (login with Nafath).

Why the result varies

Wi-Fi or cable: on Wi-Fi, speed depends on the distance to the router and on walls. To measure the line itself, use a computer connected with an Ethernet cable.
Other devices: a TV streaming video or a phone updating shares the same connection.
Mobile network: on 4G and 5G, speed depends on coverage, the number of users on the mast and your plan.
Time of day: networks are busier in the evening. Run several tests at different times before drawing conclusions.

How much speed do you need?

Netflix recommends at least 3 Mbit/s for HD video (720p), 5 Mbit/s for Full HD (1080p) and 15 Mbit/s for 4K (Netflix Help Center). These speeds add up when several screens stream at the same time. For video calls and online games, latency matters as much as speed: below 50 ms, conversation feels smooth.

Official sources

Communications, Space and Technology Commission — Telecom Complaints Escalation: escalation after 5 days without resolution, within 180 days.

Indicative measurement, which depends on your device, your browser and the state of the network at the time of the test. It cannot be used as evidence against your provider.