What a packet is
Data online travels in small chunks, typically up to about 1,500 bytes each. A single web page might be hundreds of packets; a minute of video call is thousands. Each packet finds its own way across the network and is reassembled at the other end.
What packet loss does
What happens when packets go missing depends on the kind of traffic:
- Web pages, downloads, streaming (TCP): missing packets are sent again. You don’t see errors, but each resend takes time, and TCP slows down when it detects loss. Pages load slower and download speeds drop.
- Calls and games (usually UDP): there is no time to resend; by the time a replacement arrived it would be too late. The app fills the gap as best it can. You hear dropped syllables, see blocky or frozen video, or watch other players jump around.
Why packets get lost
- Congestion: when a router’s queue is full, new packets are dropped.
- WiFi problems: interference and weak signal corrupt packets in the air. WiFi retries, but sometimes gives up.
- Faulty hardware or cables: a damaged Ethernet cable, a loose coax connector or an overheating router.
- Line faults on your provider’s network, such as noise on a DSL line or a failing cable amplifier.
- Deliberate dropping: some networks drop certain traffic, or limit it, by policy.
How much packet loss is too much?
| Loss | Typical effect |
|---|---|
| 0% | Ideal. Most healthy wired connections show none in a short test. |
| Under 1% | Rarely noticed outside calls and games. Microsoft’s Teams guidance targets under 1%. |
| 1–2.5% | Noticeable glitches in calls and games; slower downloads over long distances. |
| Over 2.5% | Real-time apps struggle badly; the connection feels unreliable. |
Loss often comes in bursts. A connection can show 0% in one test and 3% a few minutes later. Several tests over a day give a fairer picture.
How a speed test measures packet loss
Because normal web requests hide loss by resending, our test uses a different route: WebRTC, the technology browsers use for calls. It opens a UDP connection through a TURN relay server on Cloudflare’s network, sends 1,000 numbered packets, and counts how many come back. If the UDP connection can’t be made, which happens on some networks, VPNs and firewalls, the result says “not available” instead of guessing.