Bufferbloat Test
Bufferbloat is what happens when a busy connection makes everything else lag: fast downloads, but calls freeze and pings jump. This test measures your latency when idle, then while downloading and while uploading, and shows the increase.
Free, no signup. Lightweight — the basic test uses only tiny requests.
Customize: goal, connection type
Connected via (optional — sharpens the diagnosis)
What the test does
The difference between loaded and idle median latency is the increase. A large increase suggests that when the network is busy, queues fill up and everything waits behind them — a pattern commonly associated with bufferbloat.
Data use: the advanced test transfers test data in both directions for about 8 seconds each and stops early at 300 MB per direction. On a fast connection that can be a few hundred megabytes, so avoid it on metered data.
Idle latency
Latency for 8 seconds with nothing else running — your baseline.
Download-loaded latency
Latency for 8 seconds while we download test data over several parallel streams.
Upload-loaded latency
Latency for 8 seconds while we upload test data.
How to read the increase
These bands are practical guidance, not scientific boundaries. Our test may not fully saturate very fast connections, so it can under-report bufferbloat on gigabit lines.
| Increase under load | Practical reading |
|---|---|
| Under ~30 ms | Low — queues are well controlled |
| ~30 to 100 ms | Moderate — may be noticeable in games and calls while someone downloads |
| Over ~100 ms | High — commonly associated with bufferbloat |
Fixing bufferbloat
Enable smart queue management
Look for SQM, "Smart Queue", fq_codel or CAKE in your router; set the rate slightly below your real line speed.
Try a router that supports it
Many ISP routers do not; OpenWrt and several consumer routers do.
Cap heavy uploads
Backups and cloud sync are frequent culprits; schedule or throttle them.