Lag Check
Speed test that shows your lag
Most speed tests stop at Mbps. This one also times your line while it's busy, which is the lag you feel in games and calls, then tells you how to fix it. Want everything at once? Run the Full Checkup.
Takes about 30 seconds. Pause big downloads on other devices for an accurate result.
What this speed test measures
The test runs for about 30 seconds in your browser. It times your line while it is quiet, then again while it is busy downloading and uploading, because the difference between the two is the lag you feel in games and calls.
- Download and upload (Mbps)
- How much data your line moves each second.
- Good: About 100 down and 20 up is comfortable for most homes. 4K streaming needs 25 Mbps; a video call wants at least 3 Mbps up.
- Ping (ms)
- The round trip to a nearby server while the line is quiet.
- Good: Under 30 ms feels snappy. Up to 40 ms is great for gaming and up to 80 ms is fine for calls.
- Jitter (ms)
- How much ping changes from one packet to the next.
- Good: Under 10 ms for gaming, under 30 ms for calls. High jitter usually points at Wi-Fi.
- Lag under load (bufferbloat)
- How much ping rises while the line is busy, measured separately while downloading and while uploading.
- Good: Under 30 ms extra (grade A or A+). This is the number that explains lag when the speed looks fine.
- DNS and leaks
- How fast name lookups answer from your line, and whether your browser exposes your IP through WebRTC.
- Good: Lookups in the tens of milliseconds and no leak. A slow DNS row has its own fix guide.
Bufferbloat grades
The grade is the extra ping added while the line is busy, taken from the worse of the download and upload phases. It follows the widely used Waveform scale:
| Grade | Extra ping under load |
|---|---|
| A+ | under 5 ms |
| A | 5 to 29 ms |
| B | 30 to 59 ms |
| C | 60 to 199 ms |
| D | 200 to 399 ms |
| F | 400 ms or more |
B or worse means downloads, streams and backups in the house will cause lag for everyone. It is usually fixable at home with Smart Queue (SQM) on your router: the bufferbloat guide and the Smart Queue calculator give you the exact limits to set.
Common questions
What is a good bufferbloat grade?
A or A+. The grade is how much your ping rises while the line is busy: A+ is under 5 ms extra, A under 30 ms, B under 60 ms, C under 200 ms, D under 400 ms and F 400 ms or more. B or worse is worth fixing with Smart Queue; the bufferbloat guide shows how.
Why does my speed test look fine but games still lag?
Because Mbps measures how much data moves, not how long each packet waits. A game needs only a few Mbps but suffers when ping jumps while someone downloads or streams. That jump is lag under load, the bufferbloat grade this test adds; see high ping but fast internet.
What ping and jitter are good for gaming and video calls?
For gaming, ping under 40 ms, jitter under 10 ms and less than 30 ms extra under load is great. Video calls are fine up to about 80 ms of ping and 20 ms of jitter with at least 3 Mbps upload. The docs explain every number in your result.
How do I get an accurate speed and lag result?
Pause big downloads, streams and backups on other devices, then test on the device that has the problem. Test once on Wi-Fi and once on a cable: if the cable is much better, start with the Wi-Fi guide. Repeat at the time of day the lag happens.