Why your ping rises during large downloads

Your game runs smoothly until someone starts downloading a large file, then your ping jumps and your character lags. The download may not be using the game’s connection directly, but it can still make game traffic wait its turn.

This delay is often called bufferbloat. The Bufferbloat Test measures how much your connection’s delay grows while downloading or uploading, then gives it a grade from A+ to F. Use the result to see whether your connection slows under load and what to try next.

Test your connection under load

1. Open the Bufferbloat Test when you are not already downloading, streaming, or uploading a large file. Other traffic can affect the result.
2. Run the test and let it measure your connection while data is being downloaded and uploaded. This adds traffic on purpose, so other people using the same network may notice a brief slowdown.
3. Check the grade and compare the delay before and during the loaded parts of the test. A big increase under load matters more than the ping number on its own.
4. Repeat the test once at a quiet time. If you use Wi-Fi, try again close to the router or over Ethernet to see whether the wireless connection is adding a separate problem.

For a fair comparison, keep the device and connection method the same between tests. Don’t run a game or another speed test at the same time.

What the result means

The grade is A or B and delay changes little

Your connection handles the test’s extra traffic reasonably well. A ping spike in one game may instead come from that game’s server, a route between you and the server, Wi-Fi interference, or a temporary network issue. Check whether the lag happens in other games and whether it stops when the download does.

The grade is low and delay rises during the download

Your connection becomes much slower to respond when it is busy. The game’s small packets are waiting behind download data somewhere in the network, often in a router or modem queue. For example, a ping that rises from 25 milliseconds to 150 milliseconds under load can make aiming and movement feel delayed.

Delay rises mostly during the upload

Uploads can cause the same problem as downloads, and they can be especially disruptive when your available upload capacity is limited. Cloud backups, video calls, live streams, and sending large files may fill the upstream queue while you are gaming.

The test looks fine, but the game still lags

The test checks your connection to its test server, not to the game server. A good grade makes bufferbloat less likely, but it does not rule out a weak Wi-Fi signal, packet loss, a busy game server, or a poor route to that server. Test again while the lag is happening, and compare with another device or a wired connection.

How to reduce ping spikes during downloads

1. Pause the large transfer while you play. Pause a game download, cloud backup, or file transfer and check whether your ping settles. On Windows 11, check Settings › Windows Update for an update in progress. On macOS, check System Settings › General › Software Update. You can also pause the download in the app that started it.
2. Use Ethernet for the gaming device. A cable removes many Wi-Fi problems, such as interference and a weak signal. If Ethernet is not practical, play near the router and avoid placing it behind a TV, inside a cabinet, or next to other electronics.
3. Turn on Smart Queue Management in your router. Look in the router’s settings for SQM, Smart Queue Management, CAKE, or FQ-CoDel. These features manage busy queues so small game packets do not wait as long behind large transfers. Router menus differ, so check your router’s manual if you cannot find the setting.
4. Set a realistic speed limit if your router supports it. Some routers let you limit download and upload speeds so traffic does not completely fill the connection. Start around 90 percent of the speeds you actually get, then retest and adjust. A limit that is too low wastes bandwidth, while one that is too high may not control the queue.
5. Limit other devices’ transfers. If the lag appears when other people use the network, schedule backups and large downloads for later. A router’s traffic controls may let you prioritize a gaming device, but simple priority settings do not always reduce the delay caused by a full queue.
6. Restart the router once, then retest. A restart can clear a temporary fault, but it will not usually fix bufferbloat that returns whenever the connection is busy. If the same delay increase keeps appearing, focus on queue management or ask your internet provider about the connection.

Why a download can affect a game

Your router temporarily holds packets when data arrives faster than it can send it. This waiting area is a queue. Without good queue management, a large transfer can fill it, so a small packet from your game waits behind other data. The game does not need much bandwidth, but it does need its packets to arrive promptly.

That is why a fast download speed does not guarantee low ping while the connection is busy. The important clue is the change in delay under load, not just the maximum speed shown by a speed test.

When to contact your internet provider

If the Bufferbloat Test repeatedly shows a large delay increase on a wired connection, even when other devices are quiet, update the router firmware and check whether its model supports queue management. If it does not, a router with SQM may help. If the delay remains high with a capable router and a correctly configured limit, contact your provider. Congestion or a problem with the modem or line may be outside your home network’s control.