Bufferbloat Test
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| Date | Download | Upload | Ping | Grade | Server |
|---|
Bufferbloat is the lag that appears when your connection is busy — a video call stuttering while someone downloads a game, or a ping spike when a backup starts. This test measures ping while the line is idle, then again during download and upload, and grades the difference from A to F.
How to read your result
| Result | What it means |
|---|---|
| A — under 30 ms extra | Excellent: calls and games stay smooth while others download |
| B — 30–60 ms | Good: a little lag during heavy use |
| C — 60–200 ms | Fair: video calls may stutter when someone downloads |
| D — 200–400 ms | Poor: gaming and calls suffer under load |
| F — 400 ms or more | Very poor: the connection jams under load |
The grade compares the busiest direction (download or upload) with idle latency. See how grades work.
What causes bufferbloat
Routers and modems hold data in a queue (a buffer) when more arrives than the line can send. Large queues keep throughput high but make every new packet wait in line — so your game or call waits behind someone else's download. The fix isn't more speed; it's smarter queueing.
It's a bit like a supermarket with one till. Someone with a single item gets through quickly when the queue is short, but waits just as long as everyone else when twenty full trolleys are ahead. Your video call is the single item; the cloud backup is the trolleys.
Download vs. upload results
The test shows two loaded pings: one during download (↓) and one during upload (↑). They often differ. Upload is usually the worse one, because upload speeds are lower and the queue fills faster — which is why calls stutter when a phone starts backing up photos. The grade uses the higher of the two, since that's the one you'll feel.
How to fix it
Many modern routers have a setting called Smart Queue Management (SQM), "adaptive QoS" or similar. Turning it on — and setting it slightly below your real speed, around 90–95 % of what this test measures — usually brings the grade up by one or more letters. That small speed sacrifice lets your router, rather than the modem, control the queue.
If your router has no such option, a newer router often helps more than a faster plan. Many mesh systems and gaming routers include it. In the meantime, schedule backups and game updates for overnight, and limit upload speed in cloud apps that allow it.
What a good grade means in practice
With an A or B, someone can download a game while you're on a call or playing, and you won't notice. With a C, fast games feel the difference. With a D or F, real-time apps struggle every time the connection gets busy — and a faster plan alone rarely changes that.
Why most speed tests don't show it
A normal speed test reports ping while the line is quiet. Bufferbloat only appears when the line is full, so you need to measure latency during the download and upload — which this test does for both. Read more in what is bufferbloat, and see how it relates to jitter and gaming lag.
Getting a fair result
Pause other devices before testing, so the only load is the test itself. Then test once more while something else is running — a download on another device — to see how your connection behaves in everyday use. Use a cable if you can, so Wi-Fi doesn't add its own delay to the result.