Start here: the quick checks
Our test measures your connection against three servers in London, Coventry and Newcastle. Your browser talks to each one in turn. That means anything sitting between your device and those servers can stop the test, and it is almost never a fault with your broadband itself.
In rough order of how often they turn out to be the cause:
- Turn off any VPN or privacy relay. This is by far the most common reason a test will not run. See the section below.
- Reload the page and try once more. A single dropped connection at the wrong moment will stop a test, and a second attempt usually goes through.
- Try a different browser. If it works in one and not another, the cause is an extension or a browser setting rather than your connection.
- Pause ad blockers and privacy extensions for this site. Some block requests to any address other than the one in the address bar, which is exactly what a speed test has to do.
- Check you are not on a work or school network. Managed networks routinely block large transfers and unfamiliar servers.
- Keep the tab in front while the test runs. Phones and laptops throttle background tabs to save battery, which can stall a test partway.
If you use a VPN or a privacy relay
This deserves its own section because it causes more failed and misleading tests than everything else combined, and most people affected have no idea it is switched on.
A VPN sends your traffic through another company's server before it reaches us. So does a privacy relay, which is the same idea under a friendlier name. When that happens we do not see your broadband provider at all. We see Cloudflare, or Google, or Amazon, and the speed we measure is the speed of that tunnel rather than the speed of your line.
The result is a reading that is usually well below what you actually pay for, and often a test that does not finish. If you have run a test and the figure seemed far too low, this is the first thing to rule out.
The ones that catch people out are the ones they did not choose to turn on:
- iCloud Private Relay on iPhone, iPad and Mac. It comes with iCloud+ and is often enabled without the owner realising. Find it under Settings, your name, iCloud, Private Relay.
- Cloudflare WARP or the 1.1.1.1 app, which stays on in the background once installed.
- Google One VPN, included with some Google One plans and with certain Pixel phones.
- Browser built-in VPNs, such as the one in Opera, and privacy modes in some antivirus suites.
- Work laptops, which often route everything through a company network whether you are in the office or not.
Switch it off, reload the page, and run the test again. If we detect that your connection is arriving from one of these networks we will show a notice on the test itself, so you are not left guessing.
If the test finished but the number looks wrong
A result that is far below your headline speed is disappointing but not necessarily a fault with the test. The most common explanation by a wide margin is wifi.
Your provider sells you a speed to the router. What reaches the device in your hand is whatever survives the trip across your home, and that can be a fraction of it. Distance, walls, floors, older devices and interference from neighbouring networks all take their toll.
The way to separate the two is to test twice. Run the test on a device connected to the router with an ethernet cable, then run it again over wifi in the room you normally use. If the wired figure is close to what you pay for and the wireless one is not, your line is fine and the problem is inside your home. Our guide to boosting your home wifi signal covers what to do about it. If both figures are low, the line itself is the limit, and speeding up slow broadband works through the causes.
Also worth allowing for:
- Other people and devices. Anything streaming, downloading or backing up while you test takes a share of the result.
- Time of day. Evenings are the busiest period on most local networks. A test at 9pm can read noticeably lower than the same line at lunchtime.
- The age of the device. An older phone or laptop may not be capable of the speed your line delivers, particularly on connections above a few hundred Mb.
- Advertised speeds are averages. The figure in the advert is usually an average measured at peak time, not a guarantee for every property.
If you want to know what your line should be capable of before judging the result, check what is available at your address, and our guide to what broadband speed you really need puts figures against different households.
If it says no test servers are available
This message means your browser reached us but we could not hand back a server to test against. It is usually brief. Wait a minute or two and try again.
If it persists for more than a few minutes, that is worth telling us about, because it points at something on our side rather than yours. The form below is the fastest way to let us know.
If it gets stuck partway through
The test moves through ping, download and upload for each of the three servers in turn, so a full run takes a little while on a slower line. It transfers around 25 MB down and 10 MB up per server.
On a connection below about 10 Mb that is genuinely slow going, and what looks like a frozen test is sometimes just a large transfer in progress. Each stage now gives up on its own after a minute rather than waiting indefinitely, so the test will always finish or tell you it could not, rather than sitting there.
If it stalls at the same point every time, tell us which stage and which server name was on screen. That is usually enough for us to find it.
Your privacy when testing
Worth stating plainly, since it comes up. We store the postcode district, such as SW1A, rather than your full address. Your IP address is stored as a one way hash and never in its original form. We use it to work out which network you are on, which is how the provider field fills itself in, and that lookup happens on our own server against an offline database rather than by asking a third party.
Tell us what happened
If none of the above fixed it, this form goes straight to us. It takes about a minute and it is the only way we find out about problems that only happen on certain networks, browsers or devices.
If you reached this page straight after a test that failed, your browser will already have recorded which servers responded and which stage it stopped at. You can see exactly what that contains before you send it, and leave it out if you would rather. There is no need to give an email address unless you want a reply.
Other things you might be looking for
To try again, head back to the broadband speed test. To see how connections perform near you without running one, speeds in your area is built from tests other people have run. If your speed turns out to be the problem, check what you could save or compare broadband deals, and if you would rather stay put, our guide to negotiating a better deal covers getting more from your existing provider. For anything else, contact us.