Bufferbloat is a network performance problem where excessive buffering in routers and modems causes high and variable latency (lag) when the network is under load. You can have a 500 Mbps connection and still experience 500ms+ ping during a file download because your router's buffer is full and holding packets instead of dropping them and signalling the sender to slow down.

Why Bufferbloat Happens

Network hardware manufacturers filled routers with large buffers to prevent packet loss. But large buffers cause a different problem: when a connection is saturated, packets sit in the buffer waiting to be sent — adding hundreds of milliseconds of queuing delay. This queue grows faster than it drains, causing high, variable latency that makes gaming, video calls, and web browsing feel terrible even at high speeds.

Symptoms of Bufferbloat

  • Ping is fine when the connection is idle but spikes massively during downloads
  • Video calls break up when someone else on the network is downloading
  • Web pages load slowly even though a speed test shows fast throughput
  • Games become unplayable when someone else starts a large download

How to Test for Bufferbloat

  • Use the DSLReports Speed Test — it measures bufferbloat directly with a letter grade (A+ to F)
  • Run a download while pinging a server — if your ping jumps from 10ms to 200ms+ during the download, you have bufferbloat
  • Cloudflare's WARP speed test also measures latency under load

How to Fix Bufferbloat

  • Enable SQM (Smart Queue Management) on your router if it supports it — OpenWrt and pfSense include this feature
  • Upgrade to a router with CAKE (Common Applications Kept Enhanced) — a modern queueing algorithm that eliminates bufferbloat
  • Rate limiting — Set the router to slightly below your actual speeds so it manages the queue rather than the modem

People Also Ask

Is bufferbloat the same as high ping?
Bufferbloat causes high ping, but not all high ping is bufferbloat. Bufferbloat is specifically characterized by ping that is fine when the connection is idle but spikes under load. Consistently high ping regardless of load is more likely a routing or distance issue.

Related: Latency | Jitter | What affects internet speed