How do I change my wifi channel to stop interference?

A wifi channel is not a lane. Channel numbers on 2.4 GHz are spaced one apart but each transmission is about five numbers wide, so channels overlap heavily and a badly chosen one is worse than a busy one. This matters most in flats, terraces and student housing, where thirty networks can be audible from one sofa. It matters very little in a detached house with no near neighbours, where the cause of slow wifi is almost always distance or walls instead.

Step by step

1. Confirm it is actually interference.Interference gets worse at the times other people are at home, affects the whole flat rather than one room, and shows as high latency and stalling rather than a steady low speed. A problem that is constant and location-specific is a coverage problem, and changing channels will do nothing for it.
2. See what is around you.Install a wifi analyser app — Android and Windows have good free ones, and macOS has a built-in wireless diagnostics scan. It lists every network audible from where you stand, with its channel and its strength. Do this from where the problem is, not from beside the router.
3. Count what is on 1, 6 and 11.Ignore the exact numbers of everyone else's speeds. You want the count of strong networks on each of the three usable channels. Weak distant networks matter far less than one loud one next door.
4. Log into the router and find the wireless settings.Look for a 2.4 GHz section with a channel dropdown, usually set to Auto. Change it to whichever of 1, 6 or 11 is least contested. Save, and expect the wifi to drop for ten to thirty seconds while the radio restarts.
5. Set the 2.4 GHz channel width to 20 MHz if the option exists.A wider channel on 2.4 GHz sounds faster and in a crowded band is usually slower, because it collides with more of your neighbours. 20 MHz is the sensible setting in any flat.
6. Leave 5 GHz on automatic unless you have a reason.There are many non-overlapping channels up there and the router has to be able to move off certain ones automatically when it detects radar, which is a legal requirement. Fixing it to a specific channel can prevent that and is rarely worth it.
7. Retest from the same spot, at the same time of day.Compare like with like. A test at 3pm proves nothing about a problem that only happens at 8pm.

Tips

• Auto is not stupid, but most routers only choose a channel at startup and then never reconsider. If your neighbours moved in after your last reboot, a restart is sometimes all the change you need.
• A microwave oven transmits in the upper middle of the 2.4 GHz band at far higher power than any router. Wifi that dies for ninety seconds while something reheats is a microwave, and the fix is to use 5 GHz for anything in that room rather than to change channel.
• If your network name is the same on both bands, moving the 2.4 GHz channel does not force devices off it. Devices choose their own band.
• Older cordless phones, some baby monitors, wireless doorbells and cheap video senders all sit in the 2.4 GHz band and none of them appear in a wifi scan. If a scan shows a clear channel and the problem persists, suspect one of those.

Common mistakes

• Choosing a channel nobody is on, like 3 or 9 — It looks empty in the scan because nobody uses it, and it overlaps two busy channels at once. You end up interfering with, and being interfered with by, both.
• Changing the channel to fix a dead spot at the back of the house — Channel choice affects contention, not range. A room with no signal needs the signal moved closer, not retuned.

Questions people ask