Latency
A speed test number tells you how much data can move. It does not tell you how evenly that data arrives. That difference is why a connection with plenty of bandwidth can still produce choppy video calls.
Jitter is the variation in latency between packets. If every packet takes 28 ms to cross the network, jitter is near zero. If one takes 28 ms, the next 55 ms, then 31 ms, the average may still look fine — but real-time applications have to buffer or drop data to cope.
Why it matters
Voice and video are sensitive to timing. A video call can tolerate a fairly high but stable latency; it struggles with rapid changes. Large jitter shows up as robotic audio, frozen frames or awkward overlaps in conversation.
Bandwidth decides how much can travel. Latency and jitter decide how usable it feels.
Common causes
- Congestion on a shared or oversubscribed link.
- Wi-Fi interference or a weak signal.
- Buffering in home routers or intermediary networks.
- Route changes and uneven load balancing.
What to do
Run a test at different times of day and compare jitter, not only download speed. If jitter is consistently high, try a wired connection, move closer to the access point, or ask your provider to check the line. For calls, a stable 50 ms connection is usually better than an unstable 15 ms one.
Run a test to see your current latency and jitter.