What Is Jitter?
Jitter measures how consistent your connection is - Not just how fast. High jitter breaks calls and games even when your download speed looks fine.
Is Your Jitter Score Good?
The short version
As a rule of thumb, jitter under 5 ms is excellent and anything above 30 ms will noticeably degrade calls and games. For the full threshold breakdown by use case - Gaming, video calls, streaming - see what counts as good jitter →
The technical definition
Jitter is the standard deviation of your ping (latency) samples measured over a short window. If your connection sends five packets with round-trip times of 18 ms, 20 ms, 19 ms, 22 ms, and 21 ms, your average ping is 20 ms and your jitter is very low (the values are tightly clustered). If those same five packets return in 10 ms, 40 ms, 8 ms, 55 ms, and 27 ms, your average ping is still 28 ms but your jitter is very high.
This distinction matters because real-time applications - Voice calls, video conferencing, online games - Are far more sensitive to consistency than to raw speed. A 50 ms consistent connection is better for gaming than a 20 ms average connection that spikes to 80 ms every few seconds. See how jitter and ping differ →
What causes high jitter?
Wi-Fi interference
The most common cause of jitter in home networks. Wi-Fi shares a radio channel with neighboring networks, microwaves, Bluetooth devices, and baby monitors. When the channel gets congested, individual packets are delayed unpredictably. Switching to a wired Ethernet connection almost always eliminates this source of jitter entirely. See our Wi-Fi improvement guide →
Network congestion
When your ISP's network is heavily loaded - Typically evenings and weekends - Packets queue behind each other at routers and switches. The queue depth fluctuates, causing the round-trip time of individual packets to vary. This is the primary cause of jitter that gets worse at peak hours. If your jitter is low at 6 AM and high at 8 PM, this is almost certainly the cause. Check your ISP's performance ranking →
Router buffer bloat
Consumer routers often have large transmit buffers that fill when your connection is saturated. A full buffer means packets stack up and wait - Adding unpredictable delay to every subsequent packet. This is known as buffer bloat and is a common cause of high jitter during downloads. Running a speed test while someone else streams or downloads will reproduce this effect.
VPN overhead
VPN connections add encryption and routing overhead to every packet. Depending on the VPN protocol and server distance, this can add 5–30 ms of additional jitter. If you run a speed test over a VPN and see high jitter, try disconnecting the VPN and testing again. Run a connection quality test →
Packet loss
When packets are lost and retransmitted via TCP, the retransmission arrives significantly later than the original packet would have - Spiking jitter. If your speed test shows any packet loss, fix that first and jitter will usually improve.
How jitter is measured
Our speed test sends a series of lightweight HTTP requests to the nearest test server and records the round-trip time of each one. Jitter is calculated as the standard deviation of those samples. Read our full measurement methodology →
One measurement is a snapshot, not a verdict. Jitter is the most time-sensitive of all connection metrics - It changes with household activity, neighborhood Wi-Fi load, and ISP traffic patterns. A single low reading at lunchtime says nothing about the 8 PM video call that keeps breaking up. To diagnose properly, test at least three times: once at a quiet hour, once at peak evening time, and once while another device in the home is actively downloading. The pattern across those three readings usually points directly at the cause - Steady-high means a local network or hardware issue, evening-only means ISP congestion, and download-triggered means buffer bloat.
How to fix high jitter
- Use Ethernet instead of Wi-Fi - Eliminates the most common source of jitter immediately
- Restart your router - Clears buffer queues and refreshes the connection to your ISP
- Test at off-peak hours - Confirms whether your ISP's congestion is the cause
- Disconnect background devices - Other devices streaming or downloading contribute to buffer bloat
- Upgrade your router - Routers with QoS (quality of service) and buffer bloat mitigation handle real-time traffic far better
- Contact your ISP - If jitter is consistently high at all hours on a wired connection, the problem is upstream