What is packet loss, and why does it freeze my calls?

Everything you do online — a web page, a voice call, a game move — is chopped into small chunks called packets and sent one by one. Packet loss is the percentage of those chunks that never reach the other end.

On a healthy connection, the number is 0%. Not "close to zero". Zero. If your test shows anything above that, you have found a problem worth fixing — often one that a speed number alone would never reveal.

Why a little loss hurts a lot

Different apps cope differently:

• Web pages and downloads use TCP, which notices missing packets and resends them. You don't see corruption; you see slowness, because every retransmission is a round trip wasted. Even 1% loss can cut throughput dramatically on long-distance connections.
• Voice and video calls can't wait for a resend — the moment has passed. Apps conceal small gaps, but beyond about 1–2% you hear robotic audio, syllables vanish and video freezes.
• Online games send your actions in a stream of packets. Lost ones mean your character teleports, shots don't register, or you get "rubber-banding".

That is why a 500 Mbps connection with 3% packet loss gives a worse call than a 20 Mbps line with none.

How Speedtesty measures it

Measuring packet loss over normal web requests is impossible — TCP hides it. So Cloudflare's measurement engine opens a WebRTC connection to a Cloudflare relay (a TURN server), sends 1,000 small UDP packets in quick batches, and counts how many are echoed back. Packets still missing three seconds after the last one was sent count as lost. The result is the percentage you see on the tile.

What causes packet loss

1. Wi-Fi interference. By far the most common. Walls, distance, microwave ovens, baby monitors and dozens of neighbouring networks all corrupt frames. The router retransmits what it can; the rest is lost.
2. Faulty or loose cables. A damaged Ethernet cable or a bent coax connector introduces errors. Wiggle, reseat, replace.
3. An overloaded router. Cheap routers drop packets when their queue fills. This often shows up together with high latency under load.
4. Overheating or ageing equipment. Modems in hot cupboards misbehave.
5. Provider network problems. A damaged line to your street, a saturated cable node, a bad peering link. If loss persists on a wired connection at quiet times of day, this is the likely cause.

How to fix it

• Test over a cable. If the loss disappears, it was Wi-Fi: move the router, change channels, use 5 GHz, or add a mesh point.
• Restart modem and router. Boring, effective.
• Replace suspect cables — they are cheap.
• Check the modem's signal page, if it has one, for errors or low signal levels; your provider can read these too.
• If wired loss persists, call the provider with your numbers and the times you tested. Loss is a fault, not a feature, and they can see it from their side.

Why we show it on the main screen

Most speed tests don't measure packet loss at all, or hide it behind an "advanced" button. We think it belongs next to download and upload, because it answers the question people actually have: why does my call keep breaking up?