Why is my fibre fast on a speed test but slow on Wi-Fi?

Because the test measures two different things depending on how you run it. A wired test shows your true line speed; a Wi-Fi test shows what actually reaches your device after the wireless hop. If wired is fast and Wi-Fi is slow, your fibre is fine and the bottleneck is your Wi-Fi, usually router placement, the wrong band, channel congestion or an old router.

Should I connect to the 2.4GHz or 5GHz network?

Use 5GHz when you're close to the router; it's much faster and less congested. Use 2.4GHz for devices far away or behind several walls, where its longer range gives a more stable, if slower, connection. If your networks share one combined name, splitting them into two named networks lets you choose deliberately instead of letting the router guess.

Will a Wi-Fi extender or mesh fix my dead zones?

For a large or double-storey home, a mesh system is usually the better fix because the units work together as one network and keep speeds high. Cheap range extenders can help with simple coverage gaps but often pass on only a fraction of the speed they receive, so don't expect miracles. Where possible, wiring stationary devices straight into the router beats any wireless workaround.

Why does my internet only slow down in the evenings?

That's the classic sign of peak-time contention. In the evening your whole neighbourhood is streaming at once, and an oversubscribed ISP can't give everyone full speed. Run speed tests at midday and again at 8pm to confirm. If midday is fast and evening crawls, switching to a less oversubscribed ISP on the same fibre line often fixes it without changing the physical connection.

What is FUP and could it be throttling my 'uncapped' connection?

FUP stands for Fair Use Policy. Many 'uncapped' plans have a monthly threshold; cross it and the ISP may throttle (deliberately slow) your line until your next billing cycle. If your connection was fine early in the month and went slow later and stayed slow, even on a wired test, FUP throttling is a strong suspect. Check your plan's fine print or ask your ISP what the threshold is.

Why Is My Wi-Fi So Slow? Fixes That Actually Work

Slow Wi-Fi is usually fixable at home, and the culprit is rarely your actual internet line. This guide walks you through diagnosing the real problem step by step, starting with the single most important test: comparing a wired speed test to a Wi-Fi one.

First, Separate Your Wi-Fi From Your Line

Before you blame your ISP, work out whether the slowdown is on your internet line (the fibre or LTE connection coming into your home) or on your Wi-Fi (the wireless signal between your router and your phone or laptop). These are two different problems with different fixes, and most people confuse them.

The cleanest way to tell them apart is to run two speed tests. First, plug a laptop directly into your router with a network (Ethernet) cable and run a test. Then unplug the cable, connect over Wi-Fi standing right next to the router, and run it again. If the wired test hits the speed you pay for but the Wi-Fi test is much slower, your line is fine and the problem is your Wi-Fi. If even the wired test is slow, the problem is your line or your ISP, and no amount of router-shuffling will help.

+Wired test fast, Wi-Fi test slow = a Wi-Fi problem (placement, congestion, old router).
+Both tests slow = a line or ISP problem (FUP throttling, peak-time contention, a fault).
+Always test next to the router first, then in the problem room, so you can see how much signal you lose with distance.

Fix the Basics: Router Placement and a Quick Reboot

Wi-Fi is just radio waves, and they hate obstacles. A router shoved inside a TV cabinet, behind the couch, on the floor, or in a corner of the house will give weak signal to half your rooms. Walls, especially the thick brick and concrete common in South African homes, water (a full geyser or fish tank), and large metal objects all soak up signal.

Put the router as central and as high as you reasonably can, out in the open, away from other electronics and the microwave. If a far bedroom is the dead zone, that distance and those walls are very likely your whole problem.

And do the obvious thing first: switch the router off at the plug, wait 30 seconds, and switch it back on. Routers run for months without a break and quietly clog up; a reboot clears that and reconnects you to your ISP cleanly. Try this before anything more complicated.

+Central, high, and out in the open beats hidden and tucked away every time.
+Keep it away from microwaves, cordless phones and other routers (yours and the neighbours').

2.4GHz vs 5GHz: Use the Right Band

Most modern routers broadcast two Wi-Fi bands, and choosing the wrong one is one of the most common reasons fibre feels slow. The 2.4GHz band travels further and through more walls, but it is slower and badly congested because almost everything uses it, including your neighbours. The 5GHz band is much faster and far less crowded, but it does not travel as far or punch through walls as well.

The simple rule: when you are near the router, use the 5GHz network to get the full speed you pay for. For devices far away or in another room, 2.4GHz may connect more reliably even though it is slower. Many routers hide both behind one name and choose for you, often badly. If yours lets you, split them into two clearly named networks (for example 'Home-5G' and 'Home-2G') so you can pick deliberately. If a speed test is slow, switch bands and test again.

Channel Congestion and Old Routers

In a flat block or a dense suburb, your Wi-Fi competes with a dozen neighbouring networks all shouting on the same channels. This congestion drags everyone down, especially on 2.4GHz. Most routers let you change the Wi-Fi channel in their settings, or set it to 'Auto' so it hunts for a clearer one. A free Wi-Fi analyser app on your phone can show you which channels are busiest so you can move to a quieter one.

The other quiet killer is an old router. The free box your ISP shipped years ago, or a hand-me-down, may only support older Wi-Fi standards that cannot deliver today's fibre speeds, no matter how good your line is. If your router is several years old and your wired test is fast but Wi-Fi never is, a newer router (Wi-Fi 5, Wi-Fi 6 or later) is often the single best upgrade you can make.

+Set your Wi-Fi channel to 'Auto', or pick a quiet one a Wi-Fi analyser app shows you.
+An ageing router caps your Wi-Fi speed even on a perfect fibre line.

Big Homes: Mesh, Extenders and Wires

If your house is large or double-storey, one router in one spot will never cover everything well. A mesh Wi-Fi system uses two or three units placed around the home that work together as one seamless network, so you keep strong signal as you move from room to room. This is usually a better fix than a cheap range extender, which often passes on only a fraction of the speed it receives.

Wherever you can, use a cable. Anything that stays put, a smart TV, a desktop, a gaming console, runs faster and more reliably wired straight into the router or a mesh node. Getting those heavy devices off Wi-Fi also frees up the airwaves for everything that genuinely needs to be wireless, like phones and laptops.

When It's Not Your Wi-Fi: Peak Times, FUP and Throttling

If even your wired speed test is slow, the problem is on the line side. The most common cause is peak-time contention: in the evening, when most of your area is streaming Netflix, Showmax and DStv at once, a heavily oversubscribed ISP slows down for everyone. Run speed tests at different times of day. If you are fast at 11am and crawling at 8pm, contention is the issue, and a less oversubscribed ISP on the same fibre line can fix it without changing networks.

On so-called 'uncapped' plans, watch for a Fair Use Policy (FUP). Once you cross a monthly threshold, some ISPs throttle (deliberately slow) your connection until the next billing cycle. If your line suddenly went slow late in the month and stayed slow, suspect FUP throttling and check your plan's fine print. Finally, too many devices downloading at once, or one device hammering a big update or backup, can saturate the whole line. Pause those and test again before assuming a fault.

+Slow only at night = peak-time congestion on an oversubscribed ISP.
+Slow only late in the month = possible FUP throttling on an 'uncapped' plan.
+Always slow, all day = log a fault with your ISP; the line itself may have a problem.

Your Step-by-Step Checklist

Work through these in order and you will pin down almost any slow-Wi-Fi problem without guessing or paying for things you don't need.

+1. Reboot the router (off at the plug, 30 seconds, on).
+2. Run a wired speed test, then a Wi-Fi test next to the router, then a Wi-Fi test in the slow room.
+3. If wired is fast but Wi-Fi isn't, fix placement, switch to 5GHz up close, and change the Wi-Fi channel.
+4. Still slow on Wi-Fi? Consider a newer router or a mesh system, and wire up the devices that stay put.
+5. If even wired is slow, test at different times of day and check your plan for FUP throttling.
+6. If it's slow all day, every day, even wired, log a fault with your ISP.

Frequently asked questions

Why is my fibre fast on a speed test but slow on Wi-Fi?: Because the test measures two different things depending on how you run it. A wired test shows your true line speed; a Wi-Fi test shows what actually reaches your device after the wireless hop. If wired is fast and Wi-Fi is slow, your fibre is fine and the bottleneck is your Wi-Fi, usually router placement, the wrong band, channel congestion or an old router.
Should I connect to the 2.4GHz or 5GHz network?: Use 5GHz when you're close to the router; it's much faster and less congested. Use 2.4GHz for devices far away or behind several walls, where its longer range gives a more stable, if slower, connection. If your networks share one combined name, splitting them into two named networks lets you choose deliberately instead of letting the router guess.
Will a Wi-Fi extender or mesh fix my dead zones?: For a large or double-storey home, a mesh system is usually the better fix because the units work together as one network and keep speeds high. Cheap range extenders can help with simple coverage gaps but often pass on only a fraction of the speed they receive, so don't expect miracles. Where possible, wiring stationary devices straight into the router beats any wireless workaround.
Why does my internet only slow down in the evenings?: That's the classic sign of peak-time contention. In the evening your whole neighbourhood is streaming at once, and an oversubscribed ISP can't give everyone full speed. Run speed tests at midday and again at 8pm to confirm. If midday is fast and evening crawls, switching to a less oversubscribed ISP on the same fibre line often fixes it without changing the physical connection.
What is FUP and could it be throttling my 'uncapped' connection?: FUP stands for Fair Use Policy. Many 'uncapped' plans have a monthly threshold; cross it and the ISP may throttle (deliberately slow) your line until your next billing cycle. If your connection was fine early in the month and went slow later and stayed slow, even on a wired test, FUP throttling is a strong suspect. Check your plan's fine print or ask your ISP what the threshold is.

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