What Is Bufferbloat?
The connection problem that doesn’t show up in a plain download/upload number.
The short version
Bufferbloat is delay caused by oversized buffers in your router, modem, or ISP equipment queuing up data instead of dropping it when your connection is busy. Routers are supposed to buffer a little traffic to smooth out bursts — but many ship with buffers sized for a much faster line than the one they’re actually serving, so under load those buffers fill up and every packet waits in a long line before it’s sent. A connection with 20 ms of idle latency can spike into the hundreds of milliseconds the moment a large download or upload starts, even though the download itself is running at full speed.
Why it matters more than raw speed
Throughput and latency measure different things. A gigabit connection with bad bufferbloat will still download a file quickly, but a video call running alongside that download will stutter, a competitive game will lag, and a voice call will start cutting out — because every packet for those real-time applications is stuck behind a queue of download traffic. This is why two connections with identical Mbps numbers can feel completely different in practice: one has small, well-managed buffers, the other doesn’t.
How netgauge measures it
netgauge records your idle latency before any test traffic exists, then re-measures latency continuously while download and upload are fully saturating your connection (loaded latency). The difference between the two — how much extra delay shows up specifically because your line is busy — is the added latency, and it’s what gets graded:
| Grade | Added latency | What it means |
|---|---|---|
| A+ | < 5 ms | No perceptible bufferbloat |
| A | < 30 ms | Safe for competitive gaming |
| B | < 60 ms | Fine for calls and casual gaming |
| C | < 200 ms | Noticeable stutter under load |
| D | < 400 ms | Calls and games will suffer |
| F | ≥ 400 ms | Severe — connection is unusable while loaded |
See the full measurement methodology for exactly how idle and loaded latency are sampled.
How to fix it
- Enable Smart Queue Management (SQM) — often labeled CAKE, fq_codel, or QoS — on your router. This is the single most effective fix: it actively manages queue length instead of letting buffers grow unbounded.
- If your router doesn’t support SQM, consider one that does (many OpenWrt-, pfSense-, and EdgeOS-based routers ship CAKE built in).
- Some ISPs now ship bufferbloat-aware equipment by default — check whether your modem/router combo has a QoS or “gaming mode” setting before buying new hardware.
- A wired Ethernet connection removes Wi-Fi’s own contention and retry delay from the picture, which can look like bufferbloat but has a different cause and fix.
Check your own connection
netgauge measures added latency automatically, alongside download, upload, jitter, and per-use-case verdicts for gaming, calls, and uploads.
Test your connection →