Glossary · Performance
Packet Loss: definition, explanation, and why it matters
The percentage of network packets that fail to arrive at their destination, expressed as a percent of packets sent.
Definition
The percentage of network packets that fail to arrive at their destination, expressed as a percent of packets sent.
Plain-English explanation
Data on the internet moves in discrete packets. When a packet is dropped — by a congested router, a noisy radio link, or a faulty cable — the sender must retransmit it. That retransmission takes time and creates the stutter, lag, and rubber-banding users experience.
Even tiny rates of packet loss have outsized impact. TCP, the protocol behind most web traffic, treats lost packets as a congestion signal and slows down. Real-time protocols like UDP simply drop the missing data and move on, producing artifacts.
Real-world examples
- 1% packet loss can cut a TCP download's throughput to a fraction of the link capacity over long distances.
- In a multiplayer game, 2–3% packet loss produces the classic 'teleporting enemy' and missed-shot feeling.
Why it matters
Packet loss explains most cases where a connection has good bandwidth and good latency on average but still feels unreliable.
Localizing where loss starts — your device, your Wi-Fi, your router, or upstream — is the fastest path to a fix.
Common misconceptions
- Myth: Zero packet loss is required for a healthy connection.
Reality: Brief, occasional loss under 1% is normal and invisible to most applications. Sustained loss above 1% is the problem.
Frequently asked questions
- What causes packet loss?
- Wi-Fi interference, overloaded routers, damaged cabling, ISP congestion, and faulty hardware along the path.
- How do I test for packet loss?
- Run a sustained ping or use a packet-loss test to send hundreds of probes and report the drop rate.