What is bufferbloat, and how do you fix it?
Bufferbloat is extra delay that appears when your connection is busy, caused by network equipment holding too much data in its buffers. It makes calls freeze and games lag even on a fast plan. The best fix is a router with smart queue management (SQM). A cable connection also helps.
What it is
Routers and modems keep a waiting line, called a buffer, for data they cannot send immediately. The bufferbloat project describes the problem as latency caused by network equipment holding too much data in its buffers. Designers made buffers very large to avoid losing any packets, but a longer line means a longer wait.
Think of a supermarket checkout. If a shopper with a full trolley is ahead of you, your single item waits too. When a big download or upload fills the line, your small, urgent messages, such as a call or a game move, wait behind it.
Signs you have it
- Calls or games freeze when someone else starts a download, an upload or a video stream.
- Your ping jumps from about 20 ms to hundreds of milliseconds under load.
- Web pages feel stuck while a big transfer is running, even though the speed test number looks fine.
How SpeedUp grades it
The test measures your idle ping, then keeps pinging while it downloads. The extra delay under load gives the grade:
| Grade | Extra delay under load | What you will notice |
|---|---|---|
| A | Under 30 ms | Nothing. The connection stays responsive when busy. |
| B | 30 to 60 ms | Rarely noticeable. Fast games may show small spikes. |
| C | 60 to 150 ms | Calls and games get uneven when others use the line. |
| D | 150 ms or more | Calls and games break up whenever the line is busy. |
How to fix it
- Confirm it. Run the test two or three times, preferably on a cable. A consistent C or D means it is real.
- Turn on smart queue management. Many modern routers offer SQM, or a feature using fq_codel or CAKE. The bufferbloat project names fq_codel as the practical answer: it manages the waiting line with smarter rules than first in, first out. Most guides suggest setting the download and upload limits a little below your measured speeds, for example around 85 to 95%, so the queue forms in the router, where it is managed, and not in the modem.
- Check your router's QoS settings. If there is no SQM, look for quality of service options. Results vary. Some QoS features help and some make no difference, so test again afterwards.
- Consider a different router. If yours has no SQM or QoS options, a router that supports SQM or fq_codel is the most reliable fix. If your provider's router is locked, ask whether you can place your own router behind it.
- Use a cable for important devices. This does not remove bufferbloat, but it removes Wi-Fi delay on top of it.
- Avoid filling the upload during calls. Schedule backups and large uploads for times when nobody is on a call or in a game.
Test again after each change so you know what actually helped.