Why is my broadband slower than advertised?

Advertised broadband speeds are estimates, not a promise of what every device will see over wifi. If your wired speed is consistently well below your provider's minimum guarantee, or it has recently dropped from normal levels, that points to a line or service issue. Otherwise, the bottleneck is often wifi, device limits, or household demand.

Why is my broadband slower than advertised?

An advertised speed is the figure most customers on that product can expect to reach, measured at the router under good conditions. It isn't a guarantee, and it isn't what every laptop or phone will show over wifi in a back bedroom. Under UK advertising rules a provider can only advertise a speed that at least half of its customers can actually achieve at peak time, so the headline number is realistic, but it describes the line, not your wifi.

The single biggest reason real speeds look lower is the gap between the line and the device. Your download speed is measured in megabits per second (Mbps). The line might be delivering 500Mbps to your router, but an old phone on wifi two rooms away might only ever pull 60Mbps. Both numbers are true. The line is fine; the wifi hop is the limit.

Other everyday causes pile on top: several people streaming at once, a big download or game update running in the background, a cheap router that came free with an older deal, or a peak-time dip on a shared line. None of these mean your broadband is broken. They mean the speed you see at any moment is shaped by far more than the headline figure on your bill. The way to cut through all of it is to test properly, which is the next step.

How should I test my broadband speed properly?

A wifi speed test on your phone tells you what that phone gets in that spot, not what your line delivers. To measure the line itself, plug a device straight into the router with an ethernet cable. That removes wifi from the equation and gives you the number that actually matters for any complaint or fault report.

Run the test on a modern laptop or computer, ideally one bought in the last few years, because an old network card can cap the result on its own. Close anything that uses the connection first: cloud backups, streaming, downloads and other devices in the house. Then run a recognised test such as Ofcom's recommended checker or your provider's own tool, two or three times, and note the figures and the time of day.

Compare what you get with two numbers from your contract: the advertised speed and, more importantly, the guaranteed minimum speed. The minimum is the figure that gives you rights. If the wired result sits close to the advertised speed, your broadband is doing its job and any slowness you feel is happening between the router and your devices. If the wired result is well below the minimum, you have a service problem worth raising. Keep dated results either way, they are your evidence.

Is the problem my broadband line or my wifi?

This is the question that decides everything else, and the wired test answers it cleanly. If the speed over a cable is fast and only wifi is slow, the line is healthy and the fix sits inside your home. If the speed is slow even over a cable, the issue is the line or the service, and that is when you contact your provider.

Wifi loses speed for ordinary physical reasons. The signal weakens through walls, floors and distance, drops off sharply the further you are from the router, and gets crowded when many devices share it. Thick walls, a router hidden in a cupboard, or a home spread over several floors all take their toll. These are setup problems, not broadband faults, and they are usually fixable without changing provider.

If wired is fast but your wifi is weak in places, that is a coverage job rather than a speed job. Our guide on how to boost your wifi signal walks through router placement, choosing the right frequency band, and when mesh wifi makes sense. We won't repeat all of that here, the point for this page is simply that slow wifi is rarely the same problem as a slow line.

What speeds should I expect on FTTC and full fibre?

What counts as normal depends entirely on which technology serves your address. FTTC (fibre to the cabinet) runs fibre to the street cabinet and copper for the final stretch to your home. Because copper loses speed over distance, FTTC commonly lands somewhere between 30Mbps and 76Mbps, and the further you sit from the cabinet, the lower that figure tends to be.

Full fibre, where fibre runs all the way to the property, has no copper bottleneck. It typically offers wired speeds from around 100Mbps up to 900Mbps or 1000Mbps depending on the package, and it holds those speeds far more steadily through the evening peak. It also gives much faster upload speeds, which matters for video calls, backups and working from home.

So before deciding your broadband is underperforming, confirm what you are actually paying for. A wired result of 65Mbps is excellent on a 67Mbps FTTC line and disappointing on a 500Mbps full fibre line. You can check which technology and which speeds are available at your address on our home broadband page, then judge your real speed against the right benchmark.

When is slow broadband actually a fault?

There are a few clear patterns that point to a genuine fault rather than normal real-world variation. The first is a wired speed that sits consistently below your guaranteed minimum. The second is a sudden drop: if your line ran at its usual speed for months and then fell off a cliff, something changed, and that is worth investigating.

Other fault signals include the connection dropping out repeatedly, speeds that collapse only at certain times every day, or a line that crawls even with a single device cabled directly into the router and everything else switched off. Damaged wiring, a faulty router, a problem at the cabinet or exchange, or congestion on a shared line can all sit behind these symptoms.

None of these are things you can fix by moving the router or buying a mesh system. They sit on the network side, which means the next move is to report them with your wired test results in hand. Real-world slowness from wifi or device limits behaves differently: it varies by room and device, and it clears up the moment you plug into the router.

What should I do if my broadband speed is below the guaranteed minimum?

Start by confirming it properly. Run two or three wired speed tests on a modern device, at different times of day, with nothing else using the connection, and note the figures and dates. This is the evidence that turns a complaint into an obligation on your provider to act.

Then report the fault to your provider and quote the guaranteed minimum speed from your contract. Under Ofcom's voluntary speed codes of practice, providers that signed up must give you a clear minimum guarantee and a window, usually around 30 days, to bring a slow line back above it. If they can't fix it in that window, you can normally leave without paying an early termination charge, even mid-contract.

If your line keeps falling short and your provider keeps missing the mark, the longer-term answer is often a better connection rather than another round of repairs. If full fibre is available at your address, it removes the copper bottleneck that causes most chronic FTTC slowness. You can check what is available and what speeds you would actually get on our home broadband page, and our UK support team can talk you through the options.

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