What is bufferbloat? Why your fast internet feels slow

You pay for 200, 500 or even 1000 Mbps, yet your video freezes the moment someone in the house downloads a game update. The culprit is called bufferbloat — a problem almost every router has, but almost no speed test measures. PulseSpeed measures it automatically with every test.

What exactly happens?

Every router has a buffer: a queue where data packets are temporarily stored when more traffic arrives than the line can handle. In small amounts that is useful. But manufacturers have made buffers far too large for years. The result: as soon as your line is saturated — during a download, for example — packets pile up in that enormous queue instead of being sent immediately.

For a download this does not matter: whether a packet takes 10 or 400 milliseconds, the file arrives just as fast. But for real-time traffic it is fatal. Your voice in a Teams call that sits in a queue for 400 ms arrives too late and gets discarded. The result: robotic audio, frozen video, or a call that drops entirely.

How to recognize bufferbloat

  • Video calls stutter as soon as someone else in the house downloads or streams
  • Online games become unplayable while updates download
  • Web pages load slowly even though your speed test shows high numbers
  • Your ping is low at rest but spikes under load

That last point is exactly what our speed test measures: after the download and upload phases, we ping your connection while downloads run in the background. The difference between your idle ping and loaded ping is your bufferbloat grade. An increase below 5 ms earns an A; above 200 ms an F.

Fixing bufferbloat

  1. Enable Smart Queue Management (SQM). Modern routers support algorithms like fq_codel or CAKE that manage the queue intelligently. Look for "SQM", "Smart Queue" or "QoS" in your router settings. Set the bandwidth to roughly 90–95% of your measured speed.
  2. Do not rely blindly on your ISP's router. Many ISP routers lack SQM. Your own router (for example Ubiquiti) (or one running OpenWrt) behind the ISP modem solves this.
  3. Limit simultaneous heavy uploads. Cloud backups and sync tools (OneDrive, Google Drive) are the biggest cause of upload bufferbloat. Schedule them overnight.

Test it yourself

Run the PulseSpeed speed test and check the bufferbloat section below your result. Scoring C or lower? Enable SQM on your router and test again — the difference is often spectacular. Want to know specifically whether your connection can handle video calls? Use our Video Call Test, which simulates a real call.

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