What is jitter and why does it ruin video calls

Speed and ping are easy to think about. Jitter is the one most people ignore — and it’s the metric that explains why your speed test says you have 600 Mbps but the kid’s Zoom class still freezes every two minutes.

This post explains what jitter actually is, why it dominates the real-world feel of voice and video calls, and what to do about it.

What jitter actually is

Latency is the round-trip time of a single packet — say, 25 ms. Jitter is how much that latency varies between packets. If every packet round-trips in exactly 25 ms, your jitter is zero. If they vary between 20 ms and 80 ms, your jitter is roughly 30 ms.

A common formula is “the average absolute change in latency between consecutive packets” — that’s the one WiFi Buddy uses in its SurveyInsightsEngine. The exact math doesn’t matter much; what matters is the intuition: jitter measures unpredictability.

Why this kills video calls specifically

Video calls (Zoom, FaceTime, Google Meet, Teams) work by streaming audio and video frames in tiny packets, in order, in real time. Every receiver maintains a small buffer to absorb network unpredictability — usually a few hundred milliseconds. Packets that show up “on time” go straight into playback. Packets that show up late are either:

1. Stretched into the buffer (you hear a slight delay), or
2. Dropped entirely if they’re too late (you see a frozen frame, a robotic-voice glitch, or a “Bob, you’re cutting out” moment).

The killer combination is low average latency, high jitter. The average is fine — the speed test will pass — but the unpredictable spikes overflow the buffer and cause exactly the kind of stutter that makes you say “I think my Wi-Fi is bad?”.

A connection with 25 ms ping and 5 ms jitter feels great. A connection with 25 ms ping and 60 ms jitter feels worse than a connection with 100 ms ping and 5 ms jitter — even though the “slower” one is technically four times slower.

What causes jitter at home

Almost all home jitter is interference at the Wi-Fi layer:

• 2.4 GHz crowding. Microwaves, Bluetooth, neighbor networks, IoT devices. 2.4 GHz has only 3 non-overlapping channels and everyone in your apartment building shares them.
• Channel changes. Modern routers will hop channels if they detect interference, and during the hop you get a latency spike.
• Background traffic on your own network. A backup running, a laptop pulling a 4 GB Xcode update, a smart-TV uploading diagnostics — all eat into the same airtime your call needs.
• Distance from the AP. As signal strength drops, the radio retransmits more packets to recover from errors, and each retransmission shows up as latency variance.

The thing it’s usually not: your ISP. ISP backbone jitter on a healthy fiber/cable connection is typically 1–3 ms. If you’re seeing 30+ ms of jitter, it’s between you and the router.

How to measure your jitter

WiFi Buddy reports jitter in two places:

1. Speed Test — the post-test report includes a jitter number alongside ping. If you’re sitting in your home office and your jitter is 40+ ms, that’s your problem.
2. Survey — every walked sample contributes to a per-survey jitter calculation, surfaced in the Insights report. The stability warning fires only when jitter/median ≥ 0.5 and jitter ≥ 20 ms — so a small wobble on a healthy baseline doesn’t trigger a false alarm.

If you don’t have WiFi Buddy, run ping -c 100 8.8.8.8 from a terminal. Look at the mdev (mean deviation) value at the bottom — that’s your jitter.

How to fix it

In rough order:

1. Get on 5 GHz. This is the single biggest jitter improvement for most homes. 2.4 GHz crowding is the #1 cause of high jitter and 5 GHz is dramatically less crowded.
2. Move closer to the router or add a mesh node. Distance matters more for jitter than for raw bandwidth. A weak signal means more retransmits means more variance.
3. Pause the backup. Time Machine, iCloud Photos, and Windows Backup can saturate your upload while you’re on a call. Most apps have a “pause for an hour” option.
4. Wire the call. If you have ethernet anywhere near where you take calls, use it. A wired connection has near-zero jitter.
5. Enable QoS on your router. Most modern routers (Eero, Nest, ASUS, Netgear) have a “prioritize video calls” or “Adaptive QoS” toggle. Turn it on.

If none of those help and your jitter is still bad, you have an interference source you haven’t found yet. Run a Wi-Fi survey, see where the jitter is worst, and look for the appliance that’s sitting next to that spot. (It’s usually the microwave.)