Bufferbloat test (latency under load)
Check whether your connection "bloats" — whether ping spikes when someone at home downloads or uploads. This is the main cause of lag in games and choppy video calls.
The test fully saturates your line for a few seconds — other devices on the network may briefly slow down.
About the bufferbloat test
Bufferbloat happens when your latency shoots up the moment your connection is busy uploading or downloading. This test measures your ping while idle and then again under heavy load, so you can see how much your latency grows and grade the result from A+ to F.
High bufferbloat is the hidden cause of lag in games and stutter on video calls when someone else in the house is streaming or backing up files. If your grade is low, enabling Smart Queue Management (SQM/fq_codel) on your router usually fixes it.
Bufferbloat FAQ
What causes bufferbloat?
Oversized network buffers hold too much data during heavy traffic, delaying time-sensitive packets like game and voice data. The result is a big ping increase whenever the line is saturated.
How do I fix bufferbloat?
Enabling Smart Queue Management (SQM or fq_codel) on a capable router is the most effective fix. Setting slightly lower bandwidth limits in your router can also reduce the problem.
What is a good bufferbloat grade?
An A or A+ grade means your latency barely rises under load, which is ideal for gaming and calls. Grades of C or lower mean you will likely notice lag when the connection is busy.