Bufferbloat: why ping rises when someone downloads something.

By Something Just Lagged · Published October 1, 2026 · Updated October 2, 2026

The speed test shows your whole plan, yet the game stutters every time someone at home starts a download, a backup or a video call. That is the bufferbloat pattern: data waiting in a queue, which makes the ping rise when the connection is full.

What bufferbloat is

Routers, modems and ISP equipment keep data they cannot send right away in a queue. With the connection idle, the queue stays empty. With the connection full, it grows, and every packet waits its turn: the ping rises, sometimes by hundreds of milliseconds, with no packet loss and with the plan's full speed arriving.

How to recognize it

The classic sign is lag that starts and stops with the traffic. It shows up when someone downloads a file, uploads photos or videos to the cloud or joins a video call, and goes away when that ends. Many speed tests miss the problem, because they show only the speed, not the ping during the test.

1. Measure the idle and full ping by hand

Open Command Prompt and run ping -t 1.1.1.1. With the internet idle, note the typical response time. Without closing the window, start a large download or upload a heavy file and compare. Press Ctrl+C to stop: Windows shows the minimum, the maximum and the average.

If the ping goes from a few tens of milliseconds to hundreds while the connection is full, the queue is big. Repeat the test in another window with your router's address, which ipconfig lists as Default Gateway. If only the external ping rises, the queue is usually beyond the router; if the router's ping rises too, look inside the home, such as the Wi-Fi.

2. Let the app repeat the test every day

In the automatic speed test, the app pings the router and the internet with the connection idle, during the download and during the upload. The 30-day history PDF gives the Ping rise under load, in milliseconds, with the median of all tests and of each period of the day. That shows whether the queue gets worse in the evening, when the ISP's network is busier. The PDF also lists the 40 most recent tests with the external ping in the three phases; earlier ones stay in the daily summaries in the app's data folder.

To repeat it right away, after changing a setting, use Test speed now in the tray menu. Automatic speed test: how much of your plan actually arrives.

3. What you can adjust

The app measures and records, but it does not change network settings or reduce ping. The fix is in the equipment: many routers have QoS or SQM (Smart Queue Management), which organizes the queue and tends to help when the speed is capped a little below what the test measured. Backup and cloud programs can also limit their upload speed.

After each change, run Test speed now and compare the ping rise with the earlier measurements. If the router belongs to the ISP and has no such setting, the record is useful for the support ticket. How to file an ISP complaint with evidence.

What the test shows — and what it does not

The test fills the connection from this PC, against the app's server at the nearest Cloudflare location, for up to 8 seconds in each direction. If the lag happens when another device downloads something, the test shows whether the queue exists, not who causes it. The ping rise is a clue to a queue, not a diagnosis of the responsible equipment.

If the ping rises but pings are also lost, or swing a lot, look at those two signs. Packet loss: how to measure it, where it happens and how to prove it. High jitter: what it is, how to measure it and when it gets in the way.

To record the moment the game stutters, mark a lag as it happens. Game lag: how to prove the connection wobbled.