Latency, jitter and loss
- Latency: the time for a small request to reach the server and the answer to come back. Under 30 ms is excellent, under 100 ms is fine for almost everything.
- Jitter: how much latency changes from one request to the next. Calls and games stutter when it goes above about 30 ms.
- Unanswered requests: requests that failed or took over two seconds. Any at all point to Wi-Fi interference, an overloaded link or a faulty connection.
This is not a ping
A browser cannot send ICMP ping packets. Each sample is an HTTPS request over an existing connection, timed with the browser's Resource Timing from request sent to first byte received, minus the server's own processing time. The number is usually a few milliseconds above a ping to the same server. Packet loss on TCP shows up as delay rather than missing answers, because lost packets are resent.
Questions
- Why is my latency higher on Wi-Fi?
- Wi-Fi shares airtime between devices and retries when there is interference, adding a few to tens of milliseconds and a lot of jitter. A cable removes most of it.