Wi-Fi has been fighting interference and airtime issues since it was first invented, and one of the tools used is the auto channel scan inside your router. This checks for nearby broadcasters, their signal strength and center channel used, and then adjusts the channel your router is using for each of its wireless bands to reduce the chance of your signal being interfered with.

That's the theory, anyway, but in practice, this automatic scan could end up using a channel that underperforms, making your Wi-Fi weaker than it should be. While it might not directly affect speed, the channel selection is designed to make your network more reliable, which is a more important factor for everyday use.

Why your router's auto scan might be wrong

Think of that scan as a snapshot not a rolling test

To understand why your router might be selecting the wrong channel for your wireless bands, it's handy to understand a little bit more about those channels and how they're allocated. A wireless band like 5 GHz isn't one individual frequency, it's a range that is divided into "channels" or smaller portions of that frequency allocation.

Take the 2.4 GHz band, which has 100 MHz of frequency allocation, subdivided into 14 channels that are 5 MHz apart (the only exception is a 12 MHz space before channel 14). Your router might only show 11 channels, because the last three are only allowed to be used in some regions.

The only non-overlapping channels at 20 MHz width are 1, 6, and 11. That's because the router is allowed to go up or down (or both) the frequency band to make the full 20 MHz, which will cover four full 5 MHz channels. At 40 MHz width, you only get one channel that's non-overlapping to use.

Here's the rest of the frequency bands and how the channels subdivide at the supported widths (the total number of available channels depends on region):

• 2.4 GHz band: Three non-overlapping channels (1,6,11) of 20 MHz width, one non-overlapping channel at 40 MHz width
• 5 GHz band: Up to 25 non-overlapping channels at 20 MHz, 12 at 40 MHz, 6 at 80 MHz, and two or three at 160 MHz
• 6 GHz band: Up to 59 non-overlapping channels at 20 MHz, 29 at 40 MHz, 14 at 80 MHz, 7 at 160 MHz, and three at 320 MHz (320 MHz only available on Wi-Fi 7)

When your router does an automatic scan, it checks the networks being broadcast nearby, then chooses the best fit setting to reduce interference. With how prevalent Wi-Fi is, you're unlikely to get clear space on the 2.4 GHz or 5 GHz bands, but not everyone has upgraded to Wi-Fi 6E or Wi-Fi 7 to get the 6 GHz band. That means your router will likely overlap with a neighbor's signal.

It's important to remember that just because a router is broadcasting on a particular channel, it might not be broadcasting data at the same time. The auto scan might miss the times of the day when your neighbors are home and using lots of data, or vice versa, and scan when it's noisy, even if that's not the conditions at the time when you're going to use your Wi-Fi.

Manual scanning could give you better results

All you need is an app

Scanning to find the best control channel to use for your router doesn't take long. You just need an app on your computer or phone to scan for nearby access points. I'm using NetSpot here, but there are any number of alternatives if you search the app store for your device.

I like NetSpot because it shows signal strength over time while you scan. You can also heatmap your home to reduce dead zones and other issues.

Scanning my neighborhood shows me 90 networks on the 2.4 GHz band alone, which is staggering. It really shows how oversaturated that band is, and my mesh system has picked channel 6 to use because that's the least congested for me. The 5 GHz band has even more, with 142 broadcasters, but I also live near multiple airports, so my router picked channel 153 which is as far from the DFS channels shared by radar as possible.

The 6 GHz band in my area only has seven broadcasters, and plenty of space for me to choose any of the control channels as a result. The ones for 2.4 GHz and 5 GHz are the two channels I would have picked manually, but your neighborhood will have a different profile and the channels you want to pick will be different as a result.

Manual mitigation is an easy fix

Using the data from our scans makes it easy

Changing the control channel for your Wi-Fi bands is simple enough on most consumer routers. For 2.4 GHz, you want to stick to channel 1, 6, or 11. The only consideration is which of those three is less congested in your area.

On the 5 GHz band, you have more things to worry about. Channels 36, 40, 44, and 48 are more compatible but also more likely to be congested. Channels 149-165 are higher power output and less prone to interference, but not every client device supports them, so you might have connectivity issues. Channels 52-64, and 100-144 are DFS channels, shared with radar and I don't recommend using them at home.

For the 6 GHz band, 5, 21, 37, 53, 69, 85, 101, 117, 133, 149, 165, 181, 197, 213, and 229 are the "Preferred Scanning Channels," that are used for in-band discovery, so clients don't have to scan the entire frequency band. Stick to these, and if you have multiple mesh nodes or access points, use a different channel for each.

On the 2.4 GHz band, I also suggest limiting the width to 20 MHz. The devices that use 2.4 GHz nowadays don't use much data, and you are only increasing the likelihood of interference by leaving this on 40 MHz. This can be changed in your router, or in the Wi-Fi adapter settings on your computer.

To change the channel and the width for most all-in-one Wi-Fi routers*, head to the menu in the chart:

* Not every router from these manufacturers will have the setting in the same place due to UI changes over time

You don't have to stick with the wireless channels your router picks

If you're noticing issues with your wireless network, manually selecting your control channel for each wireless band might help. It's important to know it isn't a magic fix, and could make things worse as well. If the first channel you pick has issues, try the others as well. Patience is the most important aspect of network troubleshooting, and the longer you spend, the better the results.