"Change your Wi-Fi channel" is advice you'll find everywhere, and most people follow it without knowing what they're changing, then wonder why nothing improved.

Channels are worth changing in specific circumstances and useless in others. Telling the two apart is easy once you know what to look at.

What a channel is

Wi-Fi runs on frequency bands divided into numbered slices. Those slices are the channels.

One thing matters more than any other: a channel isn't a private lane. It's shared ground. If your router and your neighbour's sit on the same channel, they have to take turns speaking and taking turns costs time.

That's why a crowded channel doesn't look like weak signal. The bars stay full while pages load slowly. The same symptom is approached from another angle in the guide to full signal but slow internet.

Two bands, two different problems

2.4 GHz, narrow and busy

This band has a dozen or so numbered channels, but the count misleads: neighbouring numbers overlap each other. Only three genuinely don't: 1, 6, and 11.

Choosing channel 3 or 8 sounds like finding an empty spot. It does the opposite: instead of taking neat turns with one neighbour, you interfere with two. Partly overlapping radios can't hear each other well enough to take turns, they simply corrupt each other.

This band is also used by devices that aren't Wi-Fi at all. The sources are covered in the guide to Wi-Fi interference from other devices.

5 GHz, roomier, with conditions

5 GHz has far more channels, and at sensible widths they don't overlap. Here the problem isn't crowding but two other things:

  • Shorter range, more easily stopped by walls. The comparison is in the guide to 2.4 GHz, 5 GHz, and 6 GHz.
  • Some channels are DFS, shared with weather and aviation radar. A router must leave such a channel when it detects radar, and your network disappears for a few minutes with no explanation.

Wi-Fi that vanishes briefly at irregular hours, then returns on its own, is almost always DFS, not a failing router.

Channel width: the setting most often wrong

Channel width sets how much space each transmission occupies. Wider means faster, and easier to collide.

  • 2.4 GHz: use 20 MHz. Always. On a band this narrow, 40 MHz takes nearly half the available space and guarantees collisions with neighbours.
  • 5 GHz: 80 MHz for a normal home. Drop to 40 MHz in dense surroundings, flats, or houses packed close together.
  • 160 MHz: rarely worth it. It swallows a lot of space, usually forces you onto DFS channels, and only shows benefit on nearby devices that support it.

The rule of thumb: in a crowded environment, narrower is often faster: because what you save is waiting time, and that's worth more than a peak speed you never reach.

Check before you change

Guessing gets you nowhere here. Install a Wi-Fi scanner on your phone, the guide to Wi-Fi analyser apps covers the options, and look at two things:

  1. Which channels the networks around you use on 2.4 GHz, and how strong each one is.
  2. How strong they are relative to yours where you actually use your devices. A neighbour that's faint from where you sit isn't costing you much.

Check at a busy hour, evenings, usually. A channel map taken at ten in the morning doesn't describe the situation you're complaining about.

Then pick whichever of 1, 6, and 11 is emptiest. If all three are equally busy, changing channel won't help, and what to do instead is further down.

Changing it

  1. Open the router's admin page, how is covered in the guide to setting up a new router.
  2. Find the wireless settings, and configure each band separately.
  3. On 2.4 GHz: choose 1, 6, or 11, at 20 MHz width.
  4. On 5 GHz: leave it automatic at first. Lock to a non-DFS channel only if the network keeps disappearing briefly.
  5. Save, wait for the reboot, then use it normally for a day before judging.

Change one thing at a time. Altering channel, width, and mode together leaves you unable to tell which helped, and which made things worse.

When the channel isn't the problem

Changing channel won't help if:

  • Only one device misbehaves while the rest are fine, see the guide to Wi-Fi trouble on a single device.
  • It slows at the same hour daily across every device, wired ones included. That queue is at the provider.
  • The signal really is weak in that spot. What needs fixing is placement or the number of access points, the guide to router placement.
  • Every channel is equally crowded. In dense housing that's normal. The way out is moving as many devices as possible to 5 GHz, not shuffling 2.4 GHz.

Channels are worth checking when Wi-Fi is slow despite full signal in a crowded area. Beyond that, they're rarely the answer.

On 2.4 GHz only 1, 6, and 11 deserve consideration, at 20 MHz. On 5 GHz leave it automatic unless the network keeps briefly vanishing, that's DFS, and the fix is a non-DFS channel.

And if every channel is equally busy, stop changing them. What's left isn't a channel choice but moving devices to the roomier band.