Bufferbloat Test: Why Your Ping Spikes Under Load
Ever wonder why your game starts lagging the moment someone else in the house opens Netflix? That frustrating lag isn't always about "slow speed"—it's usually a phenomenon called Bufferbloat.
⚡ What is Bufferbloat?
Bufferbloat is high latency that occurs when your router's "buffers" (memory for data packets) get too full. Instead of dropping packets or managing traffic smartly, the router holds onto them, causing a massive delay (ping spike) in your connection.
Why Speed Tests Don't Tell the Whole Story
Most speed tests only measure your maximum bandwidth (Mbps). While bandwidth is important for downloading large files, it doesn't represent responsiveness.
A 1,000 Mbps connection with high bufferbloat will feel "laggier" during a game than a 50 Mbps connection with a clean, low-latency buffer management system.
The 'Loaded Latency' Metric
When you run a test on ScanPings, pay attention to your ping during the download and upload phases. This is your Loaded Latency. If it's much higher than your idle ping, you have bufferbloat.
How to Perform a Bufferbloat Test
- Start an Idle Test: Run a speed test while no one else is using the network. Note your base ping (e.g., 15ms).
- Monitor Ping Under Load: Watch how that ping changes during the download and upload phases.
- Good: +0ms to +15ms increase.
- Fair: +16ms to +50ms increase.
- Poor (Bufferbloat): +50ms to +500ms+ increase.
- Analyze the Results: If your ping jumps to 200ms while downloading, your router is likely mismanaging its buffers.
How to Fix Bufferbloat (Step-by-Step)
Bufferbloat is a management issue, not a hardware limitation. You don't necessarily need a "faster" plan; you need a smarter router.
1. Enable SQM (Smart Queue Management)
SQM is the ultimate cure for bufferbloat. It uses algorithms like CAKE or FQ_Codel to ensure that small, time-sensitive packets (like gaming data or DNS) jump to the front of the line, even while a 50GB file is downloading.
2. Set Up QoS (Quality of Service)
Standard QoS allows you to prioritize specific devices (like your PC or Console). While not as effective as SQM, it can help mitigate lag spikes for the most important devices on your network.
3. Avoid ISP Provided Routers
Most routers provided by ISPs (Spectrum, Comcast, AT&T) use cheap hardware with massive, unmanaged buffers. Upgrading to a modern router (like an Eero, ASUS, or anything running OpenWrt) can drastically reduce bufferbloat.
Pro Tip for Gamers
If you can't buy a new router, try limiting your download speed to 90% of your maximum capacity in your router settings. This prevents the "buffers" from ever getting 100% full, which is when bufferbloat is at its worst.
Is Your Router Causing Lag?
Run our advanced speed test and watch your ping during download to see if you have bufferbloat.
Run Free Speed Test →Frequently Asked Questions
What is Bufferbloat?
Bufferbloat is a software-related bottleneck in your networking equipment that causes high latency (ping spikes) when your connection is busy. It happens when your router buffers too many packets, causing a delay in data transmission.
How do I test for Bufferbloat?
You can test for Bufferbloat by running a speed test and watching your "Loaded Latency" or "Latency Under Load". If your ping increases significantly (e.g., from 20ms to 200ms) while downloading or uploading, you have bufferbloat.
Is Bufferbloat bad for gaming?
Yes, bufferbloat is the #1 cause of "lag spikes" and "rubberbanding" in online games. Even if you have 1,000 Mbps fiber, bufferbloat can make your game feel unplayable if someone else in your house starts a YouTube video or a download.
How do I fix Bufferbloat?
The most effective way to fix bufferbloat is by enabling SQM (Smart Queue Management) or QoS (Quality of Service) on your router. Features like "CAKE" or "FQ_CODEL" are designed specifically to eliminate bufferbloat.