You pay for a connection advertised at a certain speed. You run a test and get considerably less. The instinct is to blame the provider, and sometimes that's right, but usually the gap has a more specific cause and several of them are fixable at home.

What the advertised number means

Start here, because it's the source of most confusion. Advertised speeds have historically been the speed available to the connection under good conditions, not a guarantee of what any device experiences.

Regulators in various countries have tightened the rules — requiring average speeds at peak times, or speeds available to a defined proportion of customers — but the figure still describes the line, not your laptop.

Between the line and your laptop sit several things, each of which can lose you a substantial fraction.

Wi-Fi is usually the bottleneck

The single most common cause, and it's rarely the connection's fault.

Wi-Fi speed depends on distance from the router, walls, interference from neighbouring networks, the frequency band, and the capability of the device.

The band matters enormously. The 2.4 GHz band travels further and through walls better, and is slower and heavily congested — it's shared with microwaves, cordless devices and every neighbouring network. The 5 GHz band is much faster and doesn't penetrate walls well. Newer devices support 6 GHz, which is faster still and even shorter range.

A device sitting on 2.4 GHz two rooms from the router will not deliver a fast connection regardless of what you're paying for.

Practical test: connect a computer to the router with an ethernet cable and run a speed test. If that's close to your advertised speed, the connection is fine and your problem is Wi-Fi.

Router placement, seriously

The advice sounds trivial and the effect is large.

Routers should be central, elevated, and in the open. What actually happens is that they're installed wherever the line enters the building, which is frequently a corner, at floor level, in a cupboard, behind a television.

Water absorbs the frequencies Wi-Fi uses, so anything containing water — including people and fish tanks — attenuates signal. Metal reflects it. Concrete and brick absorb a great deal.

Moving a router from a floor-level cupboard to an open shelf in a central room can transform coverage, and it costs nothing. If the line entry point makes that impossible, a longer cable from the entry point to a better router location is an inexpensive fix.

The router itself

Provider-supplied routers vary from decent to poor, and an older one may not support the standards your connection or devices can use.

If your router is more than five or six years old it's likely limiting you. Providers will often supply a newer one on request, and buying your own is an option where the provider permits it.

Mesh systems — multiple units working together — solve coverage problems in larger or awkwardly shaped homes far better than a single powerful router, because the limitation is usually distance and walls rather than transmit power.

Contention and peak times

The part that genuinely is the provider's doing.

Networks are shared. The capacity between your local area and the wider internet is finite, and it's dimensioned on the assumption that not everyone uses it simultaneously. When they do — typically weekday evenings — speeds drop.

How much they drop depends on how generously the provider has provisioned that capacity, which is a cost decision. This is the meaningful difference between providers offering nominally identical packages.

If your speeds are fine at ten in the morning and poor at eight in the evening, that's contention and no amount of home optimisation will fix it. Switching providers might.

The device

Frequently overlooked. An older phone or laptop may not support current Wi-Fi standards, and its wireless capability caps what it can receive regardless of everything else.

Testing on multiple devices tells you quickly whether the problem is the network or one machine.

Upload matters more than people think

Most consumer packages are asymmetric — much faster download than upload. That was sensible when consumption dominated.

It's less sensible now. Video calls, cloud backup, uploading files and working from home all depend on upload. A connection with excellent download and poor upload will feel unreliable in ways that a speed test focused on download won't reveal.

If you work from home, upload speed is worth prioritising when choosing a package, and it's the figure that's usually buried in the small print.

How to complain effectively

If you conclude the provider is at fault, document it. Wired speed tests, at several times of day, over a week, recorded with timestamps.

That evidence matters because most regulatory frameworks give you rights if a provider fails to deliver a minimum guaranteed speed, and those rights usually require the provider to be given a chance to fix it first. A log of wired tests is much harder to dismiss than a complaint that the Wi-Fi feels slow.