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What is Packet Loss?

Packet loss is what happens when data you send or receive over the internet never makes it to its destination. To understand why that matters, it helps to know how internet data actually travels: rather than moving as one continuous stream, it’s broken into small chunks called packets, each sent separately and reassembled on the other end. When one or more of those packets go missing along the way, that’s packet loss.

The most common cause is network congestion. Essentially, too much data is trying to move through the same connection at the same time, so some packets get dropped. Faulty hardware, weak Wi-Fi signals, and misconfigured routers can all cause it too.

You’ve almost certainly felt packet loss without knowing that’s what it was. On a video call, it shows up as choppy audio or a frozen screen. For everyday browsing and file downloads, the underlying protocols quietly request retransmission of lost packets, so you may just notice things feeling sluggish rather than broken. Packet loss is measured as a percentage of total packets sent. Anything above 1–2% is generally enough to cause noticeable problems, and real-time applications like video calls are sensitive to even less than that.

If you suspect packet loss is slowing you down, an internet speed test can help you get a clearer picture of your connection quality. You can also run a test specifically for checking packet loss.