Internet Quality Test: Bufferbloat & Latency Under Load (South Africa)
Speed tests measure Mbps. This free test measures how your line behaves under load, grading bufferbloat, jitter and latency from A to F in your browser.
Internet Quality Test
Speed tests tell you how fast your line is. This test tells you how it behaves when the line is busy, which is what actually decides whether video calls stutter and games lag. It measures bufferbloat, jitter and latency under load against Cloudflare's South African servers.
Takes about 25 seconds. No app, nothing installed.
Measuring idle latency…
Your bufferbloat grade
What is bufferbloat?
When your line is busy, your router and your ISP's equipment queue the extra data in buffers. Oversized buffers hold packets for hundreds of milliseconds before sending them on, so everything else you do waits in that queue. That is why a video call falls apart the moment someone starts a download, even on a fast line. The test measures your latency on a quiet line, then again while deliberately filling your download and upload, and the difference is your bufferbloat.
How to read the grade
A and B mean your latency stays low even when the line is saturated, so calls, gaming and browsing keep working while other traffic runs. C means noticeable slowdowns under load. D and F mean the connection queues so badly under load that real-time apps will struggle whenever anything heavy runs. Fixed lines like fibre usually grade better than LTE and 5G, where the radio link adds queueing and jitter that you cannot tune away.
Why latency under load matters more than your Mbps
An ordinary speed test tells you how many megabits per second your line can move, but almost nothing about how it behaves the moment it gets busy. When someone starts a download or a cloud backup, your router and your ISP's equipment queue the extra traffic in buffers, and oversized buffers hold packets for hundreds of milliseconds. That queueing, called bufferbloat, is why video calls freeze and games lag on lines that look fast on paper. This test measures your latency on a quiet line, then again while deliberately saturating your download and upload, and grades the difference from A to F.
The test runs entirely in your browser against Cloudflare's edge network, which has data centres in Johannesburg and Cape Town, so South African results reflect a realistic local path. Fixed lines such as fibre usually grade better than LTE and 5G, where the radio link adds queueing and jitter you cannot tune away. If your grade is poor, the explainer under your result covers what you can do about it. You can also test your resolver with the DNS Benchmark, check your line for CGNAT with the Network Inspector, or browse all our free South African tools and calculators.
Frequently asked questions
What is bufferbloat?
Bufferbloat is latency caused by oversized buffers in your router or your ISP's network. When the line is busy those buffers fill up and hold packets in a long queue, so everything else you do waits behind the bulk traffic. It is the main reason a video call falls apart the moment someone else starts a download, even on a fast fibre line.
What is a good bufferbloat grade?
A and B are good: your latency stays low even when the line is saturated, so calls, gaming and browsing keep working while heavy traffic runs. C means noticeable slowdowns under load. D and F mean the connection queues so badly that real-time apps struggle whenever anything heavy runs on the line.
Why do my video calls freeze when someone else downloads?
Because the download fills the buffers on your line and your call's packets get stuck in that queue. A video call needs its packets delivered within tens of milliseconds, and under bufferbloat they can sit in the queue for hundreds. The fix is not more speed but better queue management, so latency under load is the number to improve.
How do I fix bufferbloat?
On a fixed line the most effective fix is a router that supports Smart Queue Management, often listed as SQM, fq_codel or CAKE, set to slightly below your line speed. Many gaming routers ship this as an anti-bufferbloat or QoS setting. On LTE and 5G connections the queueing largely happens on the radio network itself, which you cannot control, so moving latency-sensitive devices to fibre is usually the only real cure.
Is this the same as a speed test?
No. A speed test measures the maximum megabits per second your line can move, and this test measures what happens to your latency while the line is moving data. The two are complementary: a line can score 200 Mbps on a speed test and still be miserable for calls and gaming because of bufferbloat. This test does report approximate download and upload speeds as a by-product.
Why is my ping high on LTE and 5G internet?
Wireless connections add latency in the radio link itself, and the network schedules and queues traffic for many users on the same tower. That makes both idle ping and jitter higher than fibre, and latency under load can climb steeply when the tower or your line is busy. It is a property of the technology, so if low ping matters, fibre is the better choice where available.
How much data does the test use?
Up to about 150 MB, because the only honest way to measure your line under load is to genuinely load it with real downloads and uploads. On an uncapped fibre line this is nothing to worry about. On a capped mobile or LTE plan, run it sparingly and keep the cap in mind.
What is jitter?
Jitter is how much your latency varies from moment to moment. A connection with 20 ms ping that swings between 5 ms and 80 ms feels far worse on calls and in games than a steady 30 ms line, because real-time apps have to buffer for the worst case. Low, stable latency beats occasionally low latency every time.