What is bufferbloat — and how to fix it
Your internet can be fast and still feel slow. Bufferbloat is the hidden latency that only shows up when the line is busy. This page explains what it is, why your router causes it, how to test for it, and the one setting that fixes it on every platform. As of 2026-11.
The one-minute version
When you download at full speed, your router fills its buffer (the queue where packets wait). While that queue is full, every other packet — a game, a video call, a DNS lookup — waits in line behind it. That added wait is bufferbloat. It is the reason your connection is "fine" when you test it at night, then lags the moment someone streams or downloads in the morning.
Why your router causes it
Modern routers ship with large buffers because a big queue looks good in a speed test (the queue hides how fast the hardware is). But a big queue is exactly what hurts real-time traffic: the longer the queue, the longer every new packet waits. This is a property of the router's queue management, not your internet speed — which is why upgrading the plan often does not help.
How to test for it
Bufferbloat is a property of your line under load, so you must measure latency while the line is saturated, then compare to idle. Two ways:
- Our in-browser test — the NetSteer bufferbloat test measures idle and loaded latency right in the browser and scores the gap.
- Waveform — the community reference benchmark (hosted, donation-backed). How to use it vs NetSteer →
The signal you are looking for: a small, stable idle latency that jumps to hundreds of milliseconds once a download starts.
The fix: SQM with CAKE
Enable Smart Queue Management (SQM) on your router and use the CAKE queue discipline. SQM paces traffic to your measured upstream speed, which keeps the queue near-empty, so a background download no longer monopolises the line. Two settings matter:
- Set SQM to your real upstream bandwidth (not the advertised number).
- Route latency-critical traffic (games, calls, DNS) through the slow path so it gets priority.
The good news: once it is on, you usually never think about it. The bad news: it is buried in every router's menus. On OpenWrt, NetSteer turns it on in a single toggle and configures it for you — OpenWrt SQM guide. The rest of the page covers the other platforms.
Step-by-step fix guide for every platform →
By platform
SQM + cake, full control. NetSteer automates OpenWrt. Best results.
Enable "QoS" if present; often limited. A mesh/router with CAKE support is the real fix.
Excellent — add RPS/IRQ spread (NetSteer's RPS feature) to avoid single-core receive bottleneck.
How much is "too much"?
| Added latency | Reading | Action |
|---|---|---|
| ≤ 20 ms | Good | Keep SQM/CAKE on; you are well-provisioned. |
| 20–50 ms | Fair | Enable SQM, slow path for real-time. |
| 50–150 ms | High | SQM + cap the queue; check your measured upstream. |
| > 150 ms | Severe | Classic bufferbloat. SQM/CAKE + a CAKE-aware router. |
FAQ
Why is my internet slow when someone else is downloading?
Because your router buffers. When the line is near capacity, a large buffer builds up and every new packet (a game tick, a video-call frame) waits behind the download. This is bufferbloat — the fix is queue management (SQM/CAKE) that keeps the buffer small by pacing to your real speed.
Is bufferbloat the same as high ping?
Not always. Baseline ping (idle) is set by your physical distance to the server. Bufferbloat is the added latency under load. You can have low idle ping and still have hundreds of milliseconds of lag the moment a download starts — that gap is bufferbloat.
How much bufferbloat is acceptable?
Under ~20 ms of added latency is excellent (typical with CAKE/SQM active). 20–50 ms is fair; 50–150 ms is clearly bad; above 150 ms is severe and makes real-time apps feel broken during any concurrent traffic.
Does a faster internet plan fix bufferbloat?
Usually no. A faster plan with a large router buffer can be worse for latency, because more data fills the queue. Bufferbloat is about queue management, not raw bandwidth. Enabling SQM is the real fix.