High jitter: what it is, how to measure it and when it gets in the way.
A low average ping does not guarantee a stable connection. Jitter is the change in response time from one ping to the next, and it is what makes a call break up and a game stutter even when the average looks good.
What jitter is
The app calculates each destination's jitter as the average change in response time from one ping to the next. With responses of 20, 24, 19, 31 and 20 ms, the changes are 4, 5, 12 and 11 ms, and the jitter is 8 ms. A connection that always answers in 80 ms has an 80 ms ping and jitter close to zero.
Games, calls and streams send data at a steady pace and expect to receive it at the same pace. When the timing varies, the program either waits longer to have data on hand, and the delay grows, or throws away what arrived late, and you see a freeze or cut-off voice.
1. Start with Windows ping
Open Command Prompt and run ping -n 100 1.1.1.1. At the end, Windows shows the minimum, the maximum and the average. If the maximum is much larger than the minimum, there was variation. The command does not calculate the jitter and does not say when it happened.
2. Leave the recorder calculating
The recorder pings the router every second and three external destinations (1.1.1.1, 8.8.8.8 and 9.9.9.9) every three seconds. Each incident's report gives the jitter of the router and of each destination, next to the median and the maximum, and the latency graph shows the swings on the same timeline.
3. Compare the router with the internet
What matters is where the swings show up in the same interval:
| In the report | Where it points |
|---|---|
| Jitter is high on the external destinations, and the router is calm | The swings come from beyond the router: modem, ISP or external routes. |
| The router swings too | The stretch inside your home is a suspect: Wi-Fi, cable, network adapter or the router itself. |
| Only one external destination swings | A problem with that destination or the path to it, not general instability. |
| Jitter only rises when someone downloads or uploads | Data may be waiting in a queue, and the ping varies with it. |
The report names each case, such as High jitter, router normal and High jitter, router unstable too. It is a first reading: the report itself warns that these measurements do not identify the responsible component.
4. Change one factor at a time
Wi-Fi with a weak signal, or with many devices competing for the channel, tends to swing more than a cable. Connect the PC to the router by cable, record for a few days and compare with the earlier record. Wi-Fi or internet: how to tell which one fails.
If the jitter only rises when the connection is full, the cause may be the queue in the equipment. Bufferbloat: why ping rises when someone downloads something.
If pings are lost as well as swinging, start with the loss. Packet loss: how to measure it, where it happens and how to prove it.
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The jitter you did not mark
While the connection is up, the app saves high jitter on its own. At medium sensitivity, the default, it counts when the average swing reaches 50 ms within 30 seconds and at least two destinations are affected. At low sensitivity the limit is 80 ms, and at high, 30 ms.
A single latency spike does not count as jitter: spikes have their own rule. The limit decides what the app saves, not what is acceptable.
What the data doesn't show
The jitter measured is that of the app's pings, not your game's or your call's. With one ping every three seconds on the external destinations, swings faster than that slip between one measurement and the next; when you mark a lag, they all start being pinged every second. The records do not identify the responsible component either.
To record the moment the game stutters, mark a lag as it happens. Game lag: how to prove the connection wobbled.
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