How the test works
Idle baseline. We time small HTTP round-trips while the line is quiet — that is your true latency.
Saturated load. We start several concurrent large-file transfers to push the link close to capacity, and keep sampling latency and packet loss while it is loaded.
The gap. Loaded latency minus idle latency is your bufferbloat. The bigger and more consistent the jump, the more your router buffers are flooding interactive traffic with a large queue.
All computation happens in your browser; no speedtest server signup, no plugin. Results depend on your current network state — run it when the line is otherwise quiet for a clean reading.
What your score means
| Added latency | Reading | You will feel it |
|---|---|---|
| ≤ 20 ms | Good | Barely — SQM/CAKE is likely already active or the link is well-provisioned. |
| 20–50 ms | Fair | Noticeable in games and calls during a download. |
| 50–150 ms | High | Clear bufferbloat — background traffic stalls interactive ones. |
| > 150 ms | Severe | Classic "bufferbloat" — enable SQM and cap the queue. |
How to fix bufferbloat
The standard fix is queue management (SQM with the cake plugin): it keeps the router’s queue near-empty by pacing traffic to your real bandwidth, so a background download stops monopolising the line. Three things matter:
- Set SQM to your measured upstream speed (not the advertised number).
- Use the slow path for latency-critical traffic (games, calls, DNS).
- Enable it on the router, not per-device — one router buffers for everyone.
On OpenWrt, NetSteer does all of this in one toggle: it auto-configures cake for your bandwidth, spreads packet receive across all cores, and gives you a Fullcone NAT for P2P. See our OpenWrt SQM guide. What bufferbloat is and how to fix it walks through pfSense, DD-WRT and consumer routers.
Frequently asked
What is bufferbloat?
Bufferbloat is high latency that appears only when a connection is near capacity, caused by large router buffers. A line that is fast when idle can add 100–500 ms of delay for a game or video call while a background download is running. The fix is queue management (SQM/CAKE) that keeps buffers small.
How does this test work without installing anything?
It runs in your browser. We measure idle latency with small round-trip timings, then fire several concurrent large-file transfers to saturate the link, sampling latency and packet loss while it is loaded. The gap between idle and loaded latency is the bufferbloat signal.
Is a result of 100 ms bufferbloat bad?
Yes. Anything above ~30–50 ms of added full-load latency will make games laggy and calls drop during a download. Good modern links (with CAKE/SQM) stay under ~20 ms. The tool scores your result against these bands.
How do I fix bufferbloat?
Enable SQM with the cake plugin on your router (OpenWrt, pfSense, DD-WRT), set it to your measured upstream bandwidth, and use the slow path for latency-sensitive traffic. NetSteer does this in one toggle on OpenWrt. See our OpenWrt SQM guide.
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