Slow Wi-Fi? Use this checklist to fix
My Wi-Fi and Internet is slow

”The Internet is slow”

Nothing beats the words “slow Wi-Fi” for invoking fear in every work-from-home household.

If you are the unlucky one tasked with keeping the Internet and Wi-Fi running smoothly, do you know what to do?

There are lots of different kinds of problems, so naturally the troubleshooting and resolution varies too.

The non-obvious problems are sometimes the hardest. If you find yourself with “the Internet works, but seems very slow”, here’s a few things to check.

Troubleshooting slow Internet

As an engineer, I know the most important thing is to carefully isolate the problem and change only one thing at a time when trying to fix slow Wi-Fi.

The challenge is that the actual problem is often masked by the symptoms that you see and can lead you off on a tangent or in the wrong direction.

Is the computer itself having trouble?

Run different browsers (Safari, Chrome, Firefox, or Microsoft Edge) and see if the speed results are consistent.

Do all the usual of a complete reboot, clearing the browser and computer cache, and other general computer housekeeping/cleanup.

Safe mode is safe

Reboot your computer into safe mode; let it run for a few minutes; then reboot normally.

Safe mode, on both Mac and PC, will initiate cache and other cleanups that might be hard to do manually.

Remember you want to be running normally, not in safe mode, when actually doing your testing and troubleshooting, so be sure to reboot again and leave safe mode as soon as you can.

Change your login

Create a new user account on your computer. With macOS and Mac computers, many software problems that build up over time with multiple app installs and just general “bit rot”, are tied to the user account.

If you create a clean admin account and login, sometimes that is enough to clear the problem.

If that works, it points the finger as that specific computer and software as the source, rather than network equipment.

Deconstruct your network to a single computer

We all tend to forget that you can use an Internet connection without Wi-Fi and without a router.

Almost all Internet Service Providers (ISP) provided “modems” have an Ethernet connection which runs to the WAN port of your Router/Wifi equipment.

Unplug your router or Wi-Fi equipment and plug your laptop or computer directly into the ISP modem (cable modem, DSL modem, fiber termination terminal, or whatever they call the one you have).

Most ISP equipment can only have a single Ethernet device downstream, so make sure you don’t have anything, even a dumb Ethernet switch, inline.

You will also have to power down your ISP modem and power it back up to clear out the physical mac address it stores for the downstream device (usually your router).

Sometimes this can take as much as 15 minutes to change. Other times, you have to call your ISP and ask them to re-provision (force a configuration reset) from their end, so this isn’t always convenient.

But this is the best way to start. With only a single computer hardwired to your ISP provided modem, you clearly can isolate the problem as being ISP or end-user equipment.

Then start adding your equipment, router, switches, Wi-Fi, step-by-step until you find what is bogging down the speed.

Helpful tools

Although Ookla, Netflix, and other free web browser speed tests for measuring slow Wi-Fi are well known, the is worth a try.

It provides more insight into DNS and ping performance and also tests for buffer bloat of your network equipment.

It’s Wi-Fi, man!

Ubiquiti Networks, the makers of the popular UniFi prosumer network and Wi-Fi gear, have a newish smartphone app called Wi-Fi Man for Android and iOS.

It’s not a network/device management app like their existing stuff; it is more of an end-user discovery and testing app.

It provides a nice way to perform speed tests on mobile devices from an app instead of trying to navigate to a webpage on a smaller screen.

A unique capability is that if you run Wi-Fi man on two devices at the same time (two iPhones, or and iPhone and an iPad, for example), it will do a wireless speed test directly between the two devices..

This tells you the performance of your Wi-Fi network itself, as it doesn’t loop the data out to the Internet somewhere and back.

I believe these functions work even if you don’t any UniFi equipment themselves. (If you do have UniFi gear, it will provide more details on your configuration, but that just duplicates info already available in other UniFi apps/and web interfaces.)

“I feel the need (to measure) speed”

Lastly, and I think you will like this one – The “gold standard” for LAN testing is the open source program iPerf3: (yes, it is a website in France, not malware)

Originally from Linux roots, it has versions for PC and Mac too. This is a simple utility that performs different kinds of file transfer speed tests on your local network. You run the program on at least two devices and it measure the LAN speed. Like Wi-Fi Man, it tests speeds directly between two devices on your LAN.

A great way to use iperf3 is to load it on a small Raspberry Pi as the server and use a laptop as the client”.

Then move one of them around to different physical places on your network and measure the speed to see where you have slow Wi-Fi.

By “move”, I mean physically plug it into a port on your Ethernet switches in the different parts of your network.

You got the moves

Start with the server and the client both plugged into the same Ethernet switch to get a baseline speed, then move one of them upstream or downstream to another switch that is daisy-chained in and see if the speed changes appreciably.

This helps locate bad switches or bad cables between switches or specific drop lines in the wall.

If you have smart or managed Ethernet switches (unfortunately, most consumers don’t), the web interface or management software will give you a wealth of diagnostic data including the actual negotiated port speed of each port.

It’s an easy way to spot a bad cable or connector causing the link to drop down to 100mbps speed).

The error transmit and receive (TX/RX) counts can clue you in to a bad section of your network or even a bad network interface card in a computer or laptop.

Testing, testing…

Of course, it doesn’t hurt to also do physical testing of the Ethernet cables themselves.

Cable tester equipment runs from $10 to $20,000 depending upon the level of testing and whether the reports are going to be submitted for legal compliance/certification, but you get what you pay for.

Here’s a few to consider:

Dirt cheap wiring tester – less than $10

Good quality basic cable tester from a respected commercial brand for a reasonable $29

Fluke Professional cable tester/verifier – be prepared to part with some cash!

Fluke Ultimate professional tester – Spend $1300 and you can do my work for me!

Good Luck – I hope these tips are useful.


Automation technologist and problem solver

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