Ping Argus › How to test for packet loss (and why speed tests can't see it)

How to test for packet loss (and why speed tests can't see it)

Packet loss is the most destructive thing that can happen to a connection and the hardest to see. A loss rate too small to dent your speed number will make voices robotic and games rubber-band — and almost every speed test on the internet is structurally incapable of showing it to you.

Last updated 29 August 2026

Why speed tests cannot see it

Speed tests move data over TCP. TCP guarantees delivery: if a packet goes missing, it is quietly sent again, and the application never learns anything was wrong.

So loss does not appear as loss. It appears as slightly less throughput, buried inside a number that varies by more than that anyway. You can lose two per cent of your packets and see a speed test result you would call excellent.

Measuring loss honestly requires UDP with retransmission switched off, so that a packet which goes missing simply never arrives and can be counted. That is a different kind of test, and it needs a server on the far end willing to play along.

Why it matters so much more than speed

Voice and video calls are UDP. There is no re-sending — a late packet is worthless, so it is discarded. Every lost packet is a small hole in the audio, and your brain hears it as robotic, clipped speech.

Games are the same. A lost position update means the game has to guess where everything is, then correct itself when the truth arrives. That correction is what rubber-banding is.

Under 0.5% you will probably not notice. Between 0.5% and 2% calls degrade and games feel unfair. Above 2% it is obvious to everyone in the house.

Finding the cause

Wi-Fi is the most common cause by a distance. Test once with a cable, even briefly. If the loss disappears, stop looking at your provider.
On Wi-Fi, move closer and use the 5 GHz network rather than 2.4 GHz. Microwaves, baby monitors, and every neighbour crowd 2.4 GHz.
Check the cable itself if you are already wired. A damaged or cheap cable drops packets while still appearing to work perfectly.
If it is bad on every device, wired and wireless, it is the line rather than your home — and that is worth reporting, with a test result attached as evidence.

On a mobile connection

Loss on a radio is nearly always signal rather than fault. It changes over a few metres, so run the test again by a window or outdoors before concluding anything. Moving between masts on a train or in a car produces the same reading, and is not a fault at all.

Measuring yours

This site sends 300 datagrams over UDP with retransmission switched off, through a relay we run ourselves, and counts how many arrive. That number, alongside latency under load and jitter, is usually the real answer when a fast connection feels broken.

Measure it on your own line

One run, about ninety seconds. Speed, latency under load, jitter, packet loss, NAT behaviour, DNS and global reach — then an honest grade and the one thing worth fixing. Nothing to install.

Run the test

Common questions

How much packet loss is acceptable?

Under 0.5 per cent is fine and generally unnoticeable. Between 0.5 and 2 per cent, voice calls degrade audibly and games begin to rubber-band. Above 2 per cent, everyone in the house will notice.

Why does my speed test not show packet loss?

Speed tests use TCP, which silently re-sends any packet that goes missing. Loss therefore appears as a slightly lower speed rather than as loss. Detecting it requires UDP with retransmission disabled.

What causes packet loss on home internet?

Most often Wi-Fi — distance, walls, or a crowded 2.4 GHz band. After that, a damaged or low-quality cable, an overloaded router, or a genuine fault on the provider's line. Testing once over a cable separates the first two from the last.

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