Latency, bandwidth and jitter

Latency is usually measured as round-trip time in milliseconds, the 'ping'. Bandwidth is capacity, in megabits per second: a wider pipe speeds up downloads but does nothing for delay. Jitter is the variation in delay from one packet to the next, and packet loss is the share of packets that never arrive at all.

Web pages feel slow mostly because of latency rather than bandwidth. A new connection spends round trips on the TCP and TLS handshakes before any data moves, and a page may fetch dozens of files. That is why CDNs serve content from servers near the visitor, and why HTTP/2 and HTTP/3 reuse connections and cut handshake round trips. Video calls and online games feel jitter and packet loss most, so apps keep a small buffer that trades a little extra delay for smooth playback.