Quiet ping
The baseline. This is the latency / ping before the test adds intentional download or upload traffic.
technical guide
Latency under load
Latency under load measures whether a connection keeps answering quickly while it is also moving data. It is the difference between a connection that is merely fast and one that remains reliable when busy.
turn the concept into a measurement
See your own latency under load.
Bufferbloat.org compares normal latency / ping with latency during download and upload pressure, then shows the medians and chart used for the grade.
What it means
Latency is the time it takes for a small request to travel out and receive a response. Most people call this ping. A connection can have good idle ping when nothing else is happening, then become much slower as soon as a download, upload, backup, or video stream fills the line.
That loaded condition is where bufferbloat appears. Packets wait in oversized queues, so calls, games, remote desktops, and web pages feel delayed even when bandwidth still looks high.
Download load
The test downloads data and checks whether latency rises while the downstream path is busy.
Upload load
The test uploads data and checks whether latency rises while the upstream path is busy, a common weak point on home connections.
Why a bufferbloat test measures this
Bufferbloat.org compares quiet latency with download-loaded and upload-loaded latency. The score is primarily about how much latency / ping moves under stress, not how many megabits per second the connection can move.
Throughput still matters for some applications, but it answers a different question. Latency under load asks whether the network stays usable while it is busy.
Related guide
If you arrived here from a speed-test comparison, the next useful explanation is why ordinary speed tests can miss bufferbloat.