Speed test Guides

Slow Wi-Fi: the causes and the fixes that work

A 1 Gbps fibre line that tops out at 40 Mbps in the living room is almost always a Wi-Fi problem, not a plan problem. Here is how to find the cause and fix it, from the simplest step to the most technical.

Step 1: make sure it really is the Wi-Fi

Before changing anything, run two speed tests: one over Wi-Fi where you have the problem, and one with an Ethernet cable plugged straight into the router. If the wired test shows the right speed and the Wi-Fi test is slow, the problem is wireless. If both are slow, look at the line or your provider instead.

Distance and obstacles

Wi-Fi is a radio wave: it weakens with distance, and every obstacle costs you speed.

ObstacleEffect on the signal
Plasterboard wall, wooden doorLow
Brick or block wallMedium
Concrete load-bearing wall, floor between storeysHigh
Mirror, fish tank, radiator, fridgeHigh (metal and water absorb or reflect the signal)

Good habits: put the router up high, central in your home if possible, and in the open rather than inside a closed TV cabinet or behind a screen. Moving it a metre or two can double the speed in a distant room.

2.4 GHz, 5 GHz, 6 GHz: picking the right band

Recent routers broadcast on several frequency bands with different strengths:

BandRangeSpeedCongestion
2.4 GHzLong, better through wallsLimitedVery crowded (neighbours, Bluetooth, microwaves)
5 GHzMediumHighLightly used
6 GHz (Wi-Fi 6E and 7)ShortVery highAlmost empty

Near the router, prefer 5 GHz (or 6 GHz if your devices support it). Keep 2.4 GHz for distant rooms and simple smart-home devices. If your router puts all bands under one network name, it chooses automatically; if a device stays stuck on 2.4 GHz close to the router, creating two separate network names lets you force 5 GHz.

Channels and neighbours

In a block of flats, dozens of networks share the same frequencies. On the 2.4 GHz band, only channels 1, 6 and 11 don't overlap: a network set to channel 3 disturbs neighbours on both 1 and 6. Most routers pick a channel automatically at start-up; if speed collapses in the evening, restarting the router or choosing a less crowded channel manually can help. On 5 GHz, reducing the channel width from 160 to 80 MHz sometimes improves stability in dense areas.

The devices themselves

Covering a large home: extender, powerline or mesh

SolutionHow it worksStrengthsLimits
Wi-Fi extenderPicks up the signal and rebroadcasts itCheap, simpleOften halves the speed, must sit halfway
PowerlineCarries the network through power socketsGets through thick wallsDepends on your wiring, avoid extension strips
Mesh systemSeveral coordinated units, one networkEven coverage, automatic hand-overMore expensive
Ethernet cableWired link to an access pointFastest and most stableRequires running a cable

An extender placed too far from the router repeats a signal that is already weak: it needs a good signal in to give a good signal out. If you can run a cable, a second access point connected by Ethernet remains the best option.

Settings that help

  1. Restart the router from time to time: it frees memory and re-runs channel selection.
  2. Update the firmware of the router, and of any separate Wi-Fi router you use.
  3. Secure the network with a strong WPA2 or WPA3 password: a neighbour on your Wi-Fi uses your bandwidth.
  4. Move interference sources away on 2.4 GHz: microwave oven, baby monitor, some cordless phones.
  5. Wire anything that doesn't move: TV, console, desktop computer. That frees the remaining Wi-Fi for phones.

How to measure the result

Run a speed test in the same spot, at the same time of day, before and after each change, and change only one thing at a time: you'll know what really helped. Keep an eye on ping too: congested Wi-Fi often shows up as erratic latency before the speed drops.

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Frequently asked questions

Why is my Wi-Fi slower in the evening?

In the evening your neighbours use their Wi-Fi more on the same frequencies, and your provider's network is busier. Test over Ethernet: if wired is fast, it's radio congestion, and changing channel or switching to 5 GHz often helps.

Does a Wi-Fi extender double the speed?

No. It extends range, but an extender that talks to the router on the same radio often halves the available speed. It is useful for a dead zone, not for speeding up a room that already has coverage.

Is Wi-Fi 6 worth it?

It mainly improves performance when many devices are connected, and energy efficiency. You only see the benefit if your devices support Wi-Fi 6 as well.

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