Slow home Wi-Fi: the real causes and the fixes

"My Wi-Fi is slow", it's one of the most common problems people describe to me, and also the one whose cause is most often misidentified. Very often, what gets blamed on Wi-Fi is actually a device, configuration or even environmental issue. And conversely, a real network problem can sometimes be fixed in two minutes.

This guide helps you find the real cause, and apply the right fix.

First: test your connection properly#

Before hunting for causes, you have to measure. But be careful: measuring from a phone over Wi-Fi at the back of the living room won't give you the real speed of your connection, you'll also be measuring losses from distance and obstacles.

The right method in two steps:

1. Plug a computer directly into the router with an Ethernet cable, then run the test on fast.com or speedtest.net. That's your real speed, with no Wi-Fi loss.

2. Redo the test over Wi-Fi from the same spot where you're having issues. Compare the two results.

If the two measurements are similar → the problem comes from your plan or the ISP infrastructure, not the Wi-Fi.

If Wi-Fi is markedly slower than wired → it really is a wireless network problem in your home.

1. 1
   Plug an Ethernet cable directly between your computer and your router (LAN port, not the WAN port). Turn off Wi-Fi on the computer during this test.
2. 2
   Go to fast.com or speedtest.net and run the test. Note the results (download speed, upload, ping). That's the real speed of your internet connection.
3. 3
   Unplug the Ethernet cable, reconnect over Wi-Fi from the same spot where you usually run into problems. Run the test again on the same site.
4. 4
   Compare the two results: if the gap is small (less than 20%), your Wi-Fi is healthy, the issue is elsewhere. If the gap is large (Wi-Fi 2x slower or more), your wireless network is the culprit.
5. 5
   If you have access to both bands (2.4 GHz and 5 GHz), redo the Wi-Fi test on each to identify which one is affected.

The real causes of slow Wi-Fi#

1. Distance and physical obstacles#

Wi-Fi propagates like a radio wave. Walls, floors, furniture and household appliances absorb or reflect it. The further you are from the router, the weaker the signal.

The most problematic materials: reinforced concrete, breeze blocks, floor tiles, mirrors and especially metal partitions (found in some 1970s–1990s buildings).

Rule of thumb: through a concrete wall, you can lose 50 to 70% of the signal. Two walls and two floors and the Wi-Fi is often unusable.

2. 2.4 GHz vs 5 GHz: a fundamental difference#

Your router probably broadcasts on two frequency bands. Understanding the difference will help you choose which one to use.

The 2.4 GHz band is crowded by all the devices that use it: phones, tablets, smart bulbs, baby monitors, microwaves, and your neighbours' Wi-Fi. It's often the main cause of slowness in flats.

If you're close to your router, switch to the 5 GHz network in your device's Wi-Fi settings. You'll often gain 2 to 5 times the speed.

3. Wi-Fi channel saturation#

The 2.4 GHz band only has 13 channels available, of which only 3 are truly non-overlapping (1, 6 and 11). In a building of 20 flats, all the neighbours share those 3 channels. Result: traffic jam.

Your router picks a channel automatically, but not always the least crowded one.

How to see the channels in use around you:

• On Android: free "WiFi Analyzer" app
• On PC: netsh wlan show all in Command Prompt

If your router is on channel 6 and 8 neighbours are also on 6, switch manually to channel 1 or 11 in your router's settings. That single tweak can turn a mediocre connection into a smooth one.

4. A router that's too old#

Network equipment has a useful lifespan. A router more than 7–10 years old often runs on outdated Wi-Fi standards.

If your router predates 2015, it probably broadcasts in Wi-Fi 4 (802.11n). Even with fibre 1 Gbit/s from your ISP, you'll only get 150–200 Mbit/s max over Wi-Fi.

5. Too many devices connected at once#

A standard consumer router handles 10–15 devices well. Beyond that, especially if several are streaming video simultaneously, performance drops.

Count all your devices: phones, tablets, PCs, TVs, consoles, smart speakers, bulbs, thermostats, robot vacuums… In a modern home, it's not unusual to reach 25–40 permanently connected devices.

6. ISP throttling#

Some ISPs deliberately limit certain types of traffic (video streaming, peer-to-peer) at peak times. It's legal but not very transparent. To check: if your speed is normal for everything except YouTube or Netflix in the evening, that's suspicious.

DIY fixes to try first#

Before investing in hardware, try in this order:

1. Restart your router (not just the Wi-Fi, unplug the power cable for 30 seconds, plug it back in). A router can accumulate unstable states over weeks. A reboot fixes around 20% of "mysterious" issues.

2. Place your router intelligently. Ideally: up high, at the geographic centre of your home, off the floor, away from the microwave and other sources of interference. Avoid putting it behind a TV unit or in a closed cupboard.

3. Change the Wi-Fi channel in your router's interface (often accessible at 192.168.1.1 or 192.168.0.1). Switch manually to channel 1, 6 or 11 according to what WiFi Analyzer shows as the least crowded.

4. Switch to 5 GHz for devices close to the router, your PC, your TV, your console.

5. Use Ethernet for fixed devices. Your TV, your games console, your desktop PC, none of them need Wi-Fi if a cable can reach them. It frees up Wi-Fi bandwidth for mobile devices and stabilises your gaming and streaming connections.

When to invest in hardware#

If DIY fixes aren't enough, here are the hardware options in budget order:

An additional Wi-Fi access point (~€30–€80): plugged into your router via Ethernet and placed in another part of the house. Ideal for large spaces or homes with multiple floors where the router doesn't cover everything.

A Wi-Fi 6 router (~€80–€150): if your ISP router is too old, you can plug in an external router in AP (access point) mode on your existing router. The TP-Link Archer AX series, the ASUS RT-AX series or the Netgear Nighthawk are safe bets.

A mesh system (~€150–€350): several small units that talk to each other and create a unified network with no dead spots. The TP-Link Deco, Google Nest Wifi and Eero are the references. It's the ideal solution for homes of 100 m² and up with multiple floors. You're down to a single Wi-Fi network, and your phone automatically switches to the closest unit.

When to call your ISP#

The ISP is responsible for the signal up to your router, not your internal network. Call them if:

• Your speed on a direct Ethernet cable to the router is markedly below your plan
• The connection drops completely repeatedly
• Problems have existed since a network upgrade or technology change on their side (fibre rollout, etc.)

What I often see at the workshop#

One important point I want to stress: many "Wi-Fi problems" are actually device performance issues.

A laptop with a slow hard drive or not enough RAM will open web pages slowly even with a perfect fibre connection. A browser with 40 tabs and 15 active extensions will be slow even at 1 Gbit/s. A phone with saturated storage will buffer videos not because of the network, but because it can no longer process the data fast enough.

Before concluding it's the Wi-Fi, test from another device. If the problem disappears, the connection isn't at fault, your device needs attention.

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In summary#

A Wi-Fi setup that works well isn't a matter of luck, it's a matter of good configuration and equipment suited to your home.

Quick diagnosis: where is the problem coming from?#