Internet Health
Bufferbloat Test: Measure Latency Under Network Load
Bufferbloat is excessive latency caused by oversized network buffers in routers and modems. When you download a large file, bufferbloat can cause your ping to spike from 20ms to 500ms or more, making everything else on your network unusable.
Launch in Mission ControlWhat It Measures
Bufferbloat measures the difference between your idle latency (no load) and your loaded latency (during heavy traffic). A large increase indicates that your router is buffering too many packets instead of managing the queue efficiently.
How It Works
- Measures your baseline latency with 5 idle ping samples
- Starts 4 parallel download streams to saturate your connection
- Measures latency again during the active downloads
- Calculates the latency increase and assigns a grade (A+ through F)
Why It Matters
Bufferbloat is why your internet feels slow when someone else in the house is downloading or streaming. It causes video calls to freeze during file transfers, gaming lag during backups, and general sluggishness during peak usage. The fix is usually enabling SQM or QoS on your router.
Understanding Your Results
Grade A (less than 5ms increase) is excellent. Grade B (5 to 30ms) is good. Grade C (30 to 60ms) is moderate bufferbloat. Grade D or F (60ms+ increase) means serious bufferbloat that should be addressed.
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Run Bufferbloat Test Now →Frequently Asked Questions
What is bufferbloat?
Bufferbloat is a networking problem where oversized buffers in routers cause packets to queue up, dramatically increasing latency. Instead of dropping excess packets (which TCP handles gracefully), the router stores them, creating a traffic jam that affects everything on your network.
How do I fix bufferbloat?
The most effective fix is enabling SQM (Smart Queue Management) or fq_codel on your router. Many modern routers support this in their QoS settings. If your router does not support SQM, consider upgrading to one that does, such as routers running OpenWrt firmware.
Does bufferbloat affect gaming?
Absolutely. Bufferbloat is one of the primary causes of lag spikes in online gaming. When someone on your network starts a download, your gaming ping can jump from 20ms to 200ms+ if bufferbloat is present. SQM keeps gaming latency stable even under heavy load.
Can my ISP cause bufferbloat?
Yes, some ISPs have bufferbloat in their own equipment (CMTS for cable, DSLAM for DSL). While you can mitigate this with SQM on your router, ISP-side bufferbloat requires your provider to update their network equipment.
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