How Wi-Fi Actually Works, and Why Yours Slows Down

Your router broadcasts its presence periodically. When a device joins, the two negotiate a shared understanding of how they will talk: which radio band, which channel within that band, how wide that channel is, and which encryption scheme protects the traffic. From then on they take turns transmitting.

Taking turns is the important part. Wi-Fi is a shared medium, closer to a conference room than a set of private phone lines. Only one device on a given channel can transmit at a time within earshot, and devices listen before speaking to avoid talking over each other. Modern standards add scheduling techniques that make these turns far more efficient, but the underlying constraint remains.

The router then passes traffic to your modem, which connects to your internet service provider. This distinction matters for troubleshooting: Wi-Fi is the link inside your home, and your internet connection is the link out of it. A problem with one looks nothing like a problem with the other once you know to check.

Home Wi-Fi operates on a few unlicensed radio bands, and each trades range against speed. The 2.4 GHz band travels farthest and passes through walls best, but it is crowded, offers few non-overlapping channels, and supports lower speeds. It is shared with cordless phones, some baby monitors, Bluetooth accessories and microwave ovens.

The 5 GHz band offers far more channels and much higher speeds, at the cost of range and wall penetration. For most homes it is the better default for laptops, phones and streaming devices in the same room or one room away. The newer 6 GHz band, used by Wi-Fi 6E and Wi-Fi 7 equipment, adds a large amount of clean spectrum with even shorter effective range.

Most current routers present all bands under a single network name and steer devices automatically. This works well most of the time and occasionally strands a device on the wrong band. If one stationary device consistently underperforms while others are fine, band steering is a reasonable thing to suspect.

Router boxes advertise a figure that adds together the theoretical maximum throughput of every radio in the device under ideal laboratory conditions. No single client will ever see it. Real throughput depends on distance, obstacles, the capabilities of the connecting device, how many other devices are active, and how much interference is present.

A device several years old will connect at its own generation's limits regardless of how new the router is. Upgrading a router improves capacity, management of many simultaneous devices, and coverage; it does not upgrade the radio inside an older phone.

The other ceiling is the service plan itself. If your plan delivers 200 megabits per second, no router will exceed it. Wi-Fi upgrades help when the wireless link is the bottleneck, which you can confirm by comparing a speed test over Wi-Fi against one on a wired connection.

Distance and obstruction come first. Signal weakens with distance and is absorbed by materials, with masonry, tile, mirrors, metal appliances and water-filled objects among the worst offenders. A router in a corner closet on one end of the house is the single most common physical cause of poor coverage.

Congestion is second, and it has two forms. Internal congestion means many devices in your home competing for airtime. External congestion means neighboring networks on the same channel, which is why apartment Wi-Fi degrades noticeably during evening hours.

Third is device-side trouble: an outdated driver, aggressive power saving on a laptop, or a phone holding onto a distant access point instead of switching to a closer one. Fourth, and much less common than people assume, is a genuine problem with the internet service itself. Checking in that order saves a great deal of time.

Routers radiate roughly outward in all directions, so central and elevated placement covers a home far better than a corner. A shelf in a hallway near the middle of the house typically outperforms a much more expensive router hidden in a media cabinet.

Keep the unit away from large metal objects, aquariums, and directly adjacent to microwave ovens. Do not place it inside a cabinet or behind a television. External antennas, when present, generally work best positioned at different angles rather than all pointing straight up, since orientation affects coverage on different floors.

When central placement is impossible because the incoming service line terminates at one end of the house, running a single ethernet cable to a better location for the router, or to a second access point, is usually the most effective fix available. Mesh systems solve the same problem wirelessly with somewhat less efficiency.

Use WPA3 if every device supports it, or WPA2 otherwise. Older encryption schemes such as WEP are obsolete and should not be used. If your router offers a mixed mode, it will accept both and is a reasonable compromise in a household with older equipment.

Change the router's administrative password, which is separate from the Wi-Fi password and is frequently left at a factory default printed on the case. Enable automatic firmware updates if the router supports them, since firmware fixes are the main way security issues get patched.

A guest network is worth enabling. It gives visitors and smart-home gadgets internet access without placing them on the same network as your computers and file shares, which limits what a compromised device can reach.

Start by determining whether the problem is Wi-Fi or the internet connection. Run a speed test on a device connected by ethernet, or as close to the router as possible. If wired speeds are normal and wireless speeds are poor, the problem is inside your home.

Next, test in the same room as the router. If speeds are good there and bad elsewhere, you have a coverage problem, and placement or an additional access point is the answer. If speeds are poor everywhere including next to the router, restart the router and modem, then check whether one device or all devices are affected.

If only one device is affected, update its network drivers or operating system, forget and rejoin the network, and disable aggressive power saving on that adapter. If all devices degrade at predictable times of day, congestion is the likely cause, and changing channels or moving devices to a less crowded band is the appropriate response. Working through these in order will identify the cause in the large majority of household cases.