wifi speed drop

So you're paying for a 300Mbps broadband package, your phone pulls it down no problem, but your PC is sat there crawling along at 40Mbps. Frustrating doesn't cover it. I had a customer ring us last Tuesday with this exact wifi speed drop situation. Took about 20 minutes on remote support to sort. The culprit? Their PC had quietly drifted onto the 2.4 GHz band and nobody had noticed. This guide covers every cause and every fix, in order of how likely they are to actually solve it.

What Actually Causes a Wifi Speed Drop Like This?

Before you start clicking through menus, it helps to know what you're actually dealing with. A wifi speed drop from 300Mbps down to around 40Mbps isn't random. There's always a reason, and it's usually one of a small handful of things.

The biggest one, by a long way, is the band. Your router almost certainly broadcasts on two frequencies: 2.4 GHz and 5 GHz (and possibly 6 GHz on newer kit). The 2.4 GHz band tops out at around 40 to 70Mbps in real-world use. The 5 GHz band can hit 300Mbps and beyond. If Windows connects your PC to the wrong one, you'll see exactly this kind of wifi speed drop. The annoying part is that Windows doesn't always tell you it's happened. It just quietly connects to whichever band has the stronger signal at that moment, and 2.4 GHz often wins on signal strength because it travels further through walls.

Power saving is the second big cause. Windows has a setting that lets it throttle your wifi adapter to save electricity. On a laptop running on battery, that makes some sense. On a desktop, or a laptop that's always plugged in, it's just pointless and it genuinely tanks your speed. Microsoft's own documentation on fixing Wi-Fi connection issues in Windows lists power management as a primary suspect for exactly this kind of throttling.

Channel width is another one people miss. Your adapter and router negotiate a channel width when they connect. On 5 GHz, you want 80 MHz or wider. If something forces it down to 20 MHz, your throughput gets choked hard. This can happen because of a dodgy driver, a router setting, or a Windows default that nobody's changed.

Outdated drivers round out the usual suspects. The driver Windows installs automatically is often a generic Microsoft one, not the latest version from Intel, Qualcomm, Realtek, or whoever made your adapter. Older drivers can have bugs that cause exactly this kind of persistent wifi speed drop, especially after a Windows update changes something under the hood. And yes, interference from walls, distance, and neighbouring networks can contribute too, though if your phone is fast from the same spot, interference probably isn't your main problem.

Wifi Speed Drop Quick Fix: Check Your Band First

This takes two minutes and fixes the problem for a solid 40 to 50% of people who contact us about this. Do this before anything else.

More Wifi Speed Drop Fixes: Power Saving and Adapter Settings

Still getting a wifi speed drop after switching bands? Or maybe you were already on 5 GHz and the speed is still rubbish. These next fixes deal with Windows throttling your adapter from the inside. This is genuinely one of the most common things we see on remote support calls, and it's completely invisible to most users because nothing tells you it's happening.

If you're also having general network connectivity issues alongside the speed problem, our guide to fixing wifi connection problems on Windows covers some additional steps that can help, particularly around corrupted network profiles.

Advanced Wifi Speed Drop Fixes

You've tried everything above and still getting a wifi speed drop? These next steps go deeper. They're not complicated, but they take a bit more time and involve the command line. Worth doing if the intermediate fixes haven't moved the needle.

If you've got a Windows Network Reset option available (Settings, then Network and internet, then Advanced network settings, then Network reset), that's also worth trying before the hardware diagnosis step. It wipes all network adapters and reinstalls them fresh, which can clear persistent profile corruption that causes a wifi speed drop even after driver updates.

For anyone who's also dealing with slow speeds on a wired connection or general broadband issues, our slow internet speed troubleshooting guide covers the router and ISP side of things in more detail.

Preventing a Wifi Speed Drop From Happening Again

Once you've fixed it, a few habits will stop it coming back. The most important one: use separate SSIDs for your 2.4 GHz and 5 GHz networks. If they share a name, Windows will keep roaming between them and you'll be back here in a few months. Log into your router and split them. Name them something obvious like 'HomeNetwork' and 'HomeNetwork_5G'. Then connect your PC to the 5G one and leave it there.

Keep your wifi driver updated, but from the manufacturer's site, not Windows Update. Set a reminder to check every three to six months. Major Windows updates (the twice-yearly feature updates) can silently revert adapter settings back to defaults, including power saving and channel width. After any big Windows update, it's a good idea to go back into Device Manager and check your adapter settings haven't changed.

On the router side, if you're on 2.4 GHz for anything, use channels 1, 6, or 11 only. These are the non-overlapping channels. Using anything in between creates interference with neighbouring networks and degrades speeds across the board. On 5 GHz, make sure your router is set to 80 MHz channel width or Auto, not 20 MHz. The Microsoft documentation on wifi adapter PHY settings explains how Windows negotiates these parameters if you want to go deeper on the technical side.

And finally, reboot your router every couple of weeks if speeds degrade over time. Routers accumulate connection state and some do slow down without a restart. It's not glamorous advice, but it works.

Wifi Speed Drop Summary

A wifi speed drop from 300Mbps to 40Mbps almost always has a fixable software or configuration cause. Start by checking your band: if you're on 2.4 GHz, switch to 5 GHz and you'll likely see the problem disappear immediately. If you're already on 5 GHz, disable power saving in both Device Manager and Power Options, check your channel width settings in the adapter's Advanced tab, and update your driver from the manufacturer's site rather than Windows Update. If none of that works, reset the network stack with the netsh commands, try a clean driver reinstall, and if a USB adapter hits 300Mbps while the internal card stays at 40Mbps, the internal hardware is the culprit. Most wifi speed drop cases are sorted within 20 to 30 minutes using these steps.