One symptom makes people replace a perfectly good router: the internet slows at particular times, repeatedly, with nothing having changed at home.
If the pattern follows activity rather than the clock, the cause is almost always another device sharing the same frequency range.
Why this happens
The 2.4 GHz Wi-Fi band sits in a range that international rules leave open to anyone. Because it's free to use, a great many devices use it, not only Wi-Fi.
The result is that your network shares space with things that have nothing to do with the internet. Some of them are far more powerful than any router.
Nothing is broken. Not the router, not the devices, not your subscription. Two things are simply speaking on the same frequency at the same moment, and the louder one wins.
The usual suspects
| Device | How disruptive | Telltale sign |
|---|---|---|
| Microwave | Severe, within a few metres | Exactly while it's running |
| Older cordless phone | Strong | During calls |
| Baby monitor | Strong, continuous | Whenever it's on |
| Analogue security camera | Strong, continuous | Never stops |
| Bluetooth devices | Mild to moderate | During audio or file transfer |
| Smart bulbs and plugs | Mild, but numerous | Continuous, cumulative |
| Neighbouring networks | Moderate to strong | Follows the clock, not activity |
Microwaves deserve first mention because they're most often the answer and easiest to test. The door is designed to contain the waves, but a small leak suffices, and the power involved is hundreds of times a router's.
Recognising the pattern
Before changing anything, confirm this really is interference. Two patterns are often confused, and the remedies are opposite.
| Device interference | Congested network | |
|---|---|---|
| Timing | Follows activity | Follows the clock, evenings |
| Duration | Minutes | Hours |
| What's affected | Devices near the source | Everything |
| The 5 GHz band | Usually fine | Slows too |
| The fix | Change band or channel | See a different guide |
If what you're seeing matches the right column, the answer is in the guide to internet slowing at certain hours. If the signal is full but slow all the time, the cause is different again, see the guide to full signal but slow internet.
Testing it in ten minutes
Test the microwave directly
Stand near the router with a phone, run a speed test, then run the microwave with a glass of water for one minute. If the figures collapse and recover afterwards, you have your answer.
Compare the two bands
Connect to the 5 GHz network and repeat. If 5 GHz holds while 2.4 GHz collapses, the cause is definitely in the 2.4 GHz range.
Switch devices off one at a time
Baby monitor, old camera, cordless phone. Unplug, wait a minute, see whether it improves. One at a time, not all at once.
Look at what channels neighbours use
A scanner app shows how many networks are crowded onto your channel, see the guide to Wi-Fi analyser apps.
Fixing it
Ordered by effect, and none of them requires a purchase.
Move what matters to 5 GHz
This resolves most cases at once, because nearly every household source of disruption exists only at 2.4 GHz. Work laptops, TVs, and video-call devices belong on 5 GHz; leave 2.4 GHz for smart devices that genuinely don't support it.
The differences, including the shorter range, are explained in the guide to 2.4, 5 and 6 GHz.
Move the router away from the kitchen
Three metres already makes a large difference, and five usually settles it. While you're at it, consider what sits between the router and where you work, metal and water are the two worst obstacles, and a refrigerator is both.
The full considerations are in the guide to router placement.
Change channel, not router
At 2.4 GHz only three channels genuinely don't overlap: 1, 6, and 11. Other channels sound like extra options but actually create overlap with two channels at once.
Most routers pick a channel automatically, and usually do it well enough. If you set it yourself, choose one of those three, and pick whichever the scan showed to be quietest.
Reduce what's riding on 2.4 GHz
Smart plugs, bulbs, and sensors rarely need speed, but each still takes its turn to speak. In a home with a dozen smart devices, moving what can be moved to the guest network helps, and is safer too, see the guide to smart home device security.
Cable for what never moves
TVs, consoles, and desktop computers never change position. Wiring them removes them from the wireless contest entirely, see the guide to choosing LAN cable. For distant rooms where cable is impractical, the alternatives are in the guide to powerline and alternatives.
What won't help
- Raising transmit power. Your devices get louder, but the microwave is still far louder. All that increases is the router's temperature, see the guide to router overheating.
- Adding a signal booster. It extends coverage, including the coverage of the interference, see the guide to boosting Wi-Fi signal properly.
- Buying a more expensive router. A new router still shares the same frequency range with the same microwave.
- Hiding the network name. Unrelated to interference, see the guide to hiding your Wi-Fi name.
When the source isn't in your home
In dense housing and apartment blocks, the usual cause isn't kitchen appliances but neighbouring networks, sometimes a dozen, all crowded into the same range.
What you can do is limited, but real:
- Use 5 GHz wherever possible. Its range is shorter, and here that's the advantage, neighbours' signals don't reach either.
- Lower your own transmit power. Counterintuitive, but in a small space it reduces reflections and helps devices move to the nearest access point.
- Pick the quietest channel, then re-check every few months. Neighbours replace routers, and a channel that was quiet becomes crowded.
If the slowdown follows activity, appearing when something switches on, recovering when it switches off, it's interference, not congestion, and not a faulty router.
Two steps resolve most of it, both free: move important devices to 5 GHz, and move the router away from the kitchen. Replacing the router is a last resort that's almost never needed.
Frequently asked questions
Do microwaves really interfere with Wi-Fi?
Yes, and it isn't a myth. Microwaves operate in the same frequency range as 2.4 GHz Wi-Fi, and a small leak from the door is enough to drown out nearby signal for as long as it's running. The 5 GHz band is unaffected.
Which devices can interfere with Wi-Fi?
Most commonly: microwaves, older cordless phones, analogue security cameras, continuously active Bluetooth devices, and baby monitors. All operate in the same 2.4 GHz range.
Why does moving to 5 GHz solve most of it?
Almost every interfering household device operates at 2.4 GHz. The 5 GHz band is far less crowded and isn't used by kitchen appliances or older wireless gear, so the source of disruption simply disappears.
How do I tell interference from a congested network?
Interference follows devices: it appears when something switches on and stops when it switches off. Congestion follows the clock: evenings, when many people are online, with no particular device triggering it.
