Why is my Wi-Fi slow? A diagnostic order that actually works
Slow Wi-Fi usually has one cause, and it is rarely the one people try first. Work through these in order — the early steps cost nothing and catch most problems, and you avoid buying hardware you did not need.
Step 0: find out whether it is Wi-Fi at all
This takes two minutes and saves hours. Run a speed test over Wi-Fi, then plug a computer directly into the router with an Ethernet cable and run the same test.
- Wired is much faster than Wi-Fi → it is your Wi-Fi. Continue below.
- Both are slow → it is your connection or your provider, not your Wi-Fi. No amount of router tuning will help.
- Both are fine, but one device is slow → it is that device.
Skipping this step is how people end up buying a mesh system to fix a fault on the line.
Step 1: the free checks
Check what else is using the connection
A console downloading a game, a cloud backup, or someone else streaming 4K will take everything available. Pause them and retest.
Move the router
Routers do not belong in a cupboard, on the floor, behind the TV or in the corner of the house. Radio signal is absorbed by water, masonry and metal — which describes a building, its plumbing and its occupants.
Put it high, central and in the open. Moving a router from a floor-level cabinet to a shelf in a hallway routinely doubles the usable range. This is the single highest-value free change available.
Get off the microwave's frequency
2.4 GHz is shared with microwave ovens, cordless phones, baby monitors, Bluetooth and every neighbouring network. If speed drops when someone heats lunch, that is not a coincidence.
Restart properly
Power the router off for thirty seconds, not two. Enough to clear the state, not the pointless ritual it is often treated as — but do it once, not as a daily habit. A router that needs weekly restarts is a router with a fault.
Step 2: use the right band
Modern routers broadcast on two or three bands. Which one your device picks matters enormously.
| Band | Range | Speed | Use it for |
|---|---|---|---|
| 2.4 GHz | Best — through walls | Lowest, most congested | Far rooms, smart home devices |
| 5 GHz | Moderate | Much faster | Almost everything |
| 6 GHz (Wi-Fi 6E/7) | Shortest | Fastest, uncongested | Same room as the router |
The catch: many devices cling to 2.4 GHz once connected, even when 5 GHz is available and better. If your router gives both bands the same network name, you cannot control which one a device uses. Giving the bands separate names — for example Home and Home-5G — lets you put each device where it belongs. It is slightly less elegant and far more reliable.
Step 3: change channel
In a flat or a terrace you may be sharing airtime with twenty other networks. Wi-Fi devices on the same channel take turns, so a busy channel means everyone waits.
Use a Wi-Fi analyser app to see which channels are crowded, then set yours manually in the router's admin page:
- On 2.4 GHz, only channels 1, 6 and 11 do not overlap. Pick whichever of those three is least used. Anything else overlaps two of them and makes things worse for everyone, including you.
- On 5 GHz there are many non-overlapping channels. The higher ones (100+, the DFS range) are often nearly empty because cheaper routers avoid them.
Step 4: look at the device
If one laptop is slow while phones are fine, the laptop is the problem.
- Update the Wi-Fi driver. On Windows laptops this fixes a surprising share of "slow Wi-Fi" complaints, and the driver Windows Update installs is often not the latest one from the manufacturer.
- Check what the device supports. A device with Wi-Fi 4 hardware will never exceed its own limits, regardless of your router.
- Check power saving. Aggressive power management on laptops throttles the wireless adapter on battery.
- Check the VPN. A VPN adds encryption overhead and routes traffic via a distant server. Turn it off and retest.
Step 5: things worth money
Only once the free steps are exhausted:
- Run a cable. Unglamorous, cheap, and it solves the problem permanently for anything that stays in one place — a TV, a console, a desktop. It also takes that device's traffic off the airwaves, which helps everything else.
- A mesh system for a house where one router genuinely cannot cover the area. Feed the nodes with cable if you possibly can; wireless backhaul roughly halves throughput at each hop.
- A newer router if yours predates Wi-Fi 5 (802.11ac). Below that, the hardware really is the ceiling.
- Avoid powerline adapters unless nothing else is possible. They are heavily dependent on your wiring and frequently deliver a small fraction of their advertised speed.
Note that Wi-Fi extenders that rebroadcast on the same band halve your throughput and often make things worse. A mesh system with a wired backhaul is the better version of the same idea.
When it is not your Wi-Fi
If the wired test in Step 0 was also slow, the problem is upstream. Before calling your provider, gather evidence: run tests at several times of day and write down the results. Evening congestion — fine at 10am, poor at 8pm — is a specific, common and fixable complaint, and a log of timestamped results makes it far harder to dismiss.
Also check whether you are being shaped for exceeding a fair-use cap, and whether your line has been provisioned at the speed you are actually paying for. Both happen more often than providers like to admit.