What bufferbloat actually is
Bufferbloat is a phenomenon where excessive buffering in network equipment causes high latency and jitter, even on connections with fast download and upload speeds. When your router receives more data than it can immediately forward, it stores the excess packets in a memory buffer. If this buffer is too large, packets can wait in the queue for hundreds of milliseconds before being processed.
The result feels paradoxical: your speed test shows 300 Mbps, but video calls freeze, games lag, and web pages feel sluggish. This happens because the speed test measures sustained throughput (how much data flows over time) but does not reveal the queueing delay that every packet experiences when the buffer is full.
Bufferbloat is particularly severe on connections with asymmetric upload and download speeds, which includes most cable internet plans. When someone in your house starts a large upload (a cloud backup, for example), the upload buffer fills rapidly because the upload speed is much lower than the download speed. This bloated upload queue delays the small acknowledgement packets that download traffic depends on, effectively slowing everything down.
How to detect bufferbloat
The easiest way to detect bufferbloat is to compare your idle latency (ping with no other activity) against your loaded latency (ping while running a download or upload). If your idle ping is 15 ms but your loaded ping spikes to 200 ms or more, you have significant bufferbloat.
Several online tools can perform this test automatically. The Waveform Bufferbloat Test at waveform.com/tools/bufferbloat and the DSLReports Speed Test both measure latency under load. A grade of A or A+ means minimal bufferbloat; B or below indicates noticeable queueing that will affect real-time applications.
You can also detect bufferbloat through everyday symptoms: if your video call quality drops every time someone else in the house starts a download, or if game ping spikes correlate with cloud backup schedules, bufferbloat is the most likely cause.
How to fix bufferbloat
The most effective fix is enabling Smart Queue Management (SQM) on your router. SQM algorithms (like fq_codel or CAKE) actively manage the router's buffer, keeping it small and processing packets in a fair, time-sensitive order. This prevents any single device or application from monopolising the queue. After enabling SQM, loaded latency typically drops from hundreds of milliseconds to under 30 ms.
Not all routers support SQM natively. If your router does not have this feature, consider flashing it with open-source firmware like OpenWrt, which includes SQM. Alternatively, upgrading to a router that supports SQM out of the box (such as models from IQrouter, Ubiquiti, or Asus routers with Adaptive QoS) resolves the issue without technical configuration.
As a temporary workaround, you can reduce bufferbloat by limiting the speed that your router handles. Setting your router's WAN speed cap slightly below your plan's actual speed (for example, capping at 280 Mbps on a 300 Mbps plan) prevents the router's buffer from ever filling completely. This sacrifices a small amount of peak speed but dramatically improves latency under load.