Bufferbloat & Packet Loss Test
Your speed can be fast and your connection can still lag. This test checks what happens to your delay when your line is busy, and whether test requests get lost. It takes about 25 seconds.
What is bufferbloat?
When your connection is busy, your router and modem hold extra data in a queue. If the queue is too long, everything waits behind it, so delay climbs from a few milliseconds to hundreds. That extra delay is bufferbloat. It's why a video call stutters when someone starts a big download, even on a fast plan.
How to read your grade
| Grade | Extra delay under load | What it feels like |
|---|---|---|
| A+ | Under 5 ms | Excellent. Stays responsive even when busy. |
| A | 5-30 ms | Great. You won't notice it. |
| B | 30-60 ms | Good. Slight stutter in calls and games during big transfers. |
| C | 60-200 ms | Noticeable lag while the connection is busy. |
| D | 200-400 ms | Heavy lag whenever the connection is busy. |
| F | Over 400 ms | Almost unusable for calls and games under load. |
How the test works
First we measure your latency to our server on a quiet connection. Then we measure it again while your browser downloads data, and once more while it uploads. The difference between quiet and busy latency is your bufferbloat, and we grade the worse of the two directions.
About the lost-request number
Browsers can't see true packet loss, because the underlying protocol quietly resends lost packets. Instead we count test requests that fail or time out. Anything above zero is worth noting, and more than a couple of percent points to an unstable connection such as weak Wi-Fi.
How to fix bufferbloat
- Turn on Smart Queue Management in your router. Look for SQM, QoS, fq_codel or CAKE in its settings.
- Set the limits to about 90-95% of the speeds you measured on our speed test, so the queue forms in your router and not at your provider.
- Use Ethernet for gaming and calls. Weak Wi-Fi adds delay and lost requests that look like bufferbloat.
- Replace an old router that has no queue management. Many modern routers include it.
Frequently asked questions
What is bufferbloat?
Bufferbloat is the extra delay that appears when your router or modem queues too much data while your connection is busy. Your speed looks fine, but video calls and games lag whenever someone downloads or uploads.
What is a good bufferbloat grade?
A+ means under 5 ms of added latency under load, and A means under 30 ms. B (30-60 ms) is acceptable. C or worse means calls and games will lag noticeably when the connection is busy.
How do I fix bufferbloat?
Turn on Smart Queue Management (SQM, fq_codel or CAKE) in your router and set it to about 90 to 95 percent of your real speeds. If your router has no such option, a router that supports it, or limiting bandwidth slightly below your plan speed, usually helps.
Can a browser measure real packet loss?
Not exactly. Browsers use TCP, which silently resends lost packets, so true packet loss is hidden. This test counts test requests that fail or time out, which is a good sign of an unstable connection but not the same as raw packet loss.
Why is my result different from other tests?
Each test uses a different server, load and method. Ours measures against a single server, so distance affects your idle latency. The added delay under load is the number that matters most.
Why does it say "not enough load"?
To judge bufferbloat the test has to actually fill your connection. On a very slow or unstable connection the load can be too light. Try again with other devices paused.
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