Why your stream buffers when another device downloads

Your video pauses or drops in quality as soon as someone starts downloading a game, updating a computer, or copying files to the cloud. The internet may seem fast when you test it on its own, yet struggle when the household is busy.

A full download can make your router hold internet traffic in a queue, delaying the small requests that keep a stream moving. Use the Bufferbloat Test to check whether delay rises when the connection is busy, then try the fixes below.

Test the connection while another device downloads

1. Open the Bufferbloat Test on the device where you watch streams. Keep other devices quiet for a moment, then run the test to get a baseline.
2. Start a large download on another device. A game update or a large file download is useful, but avoid using a download you cannot pause.
3. Run the Bufferbloat Test again while the download continues. The test measures how much delay grows during downloading or uploading and gives a grade from A+ to F.
4. Compare the result with what you see in the stream. If possible, pause the download and test once more to see whether the delay and buffering ease.

The test adds traffic to your connection, so it can briefly affect other people using the network. Wait until nobody is relying on a call, game, or important upload before running it.

What the result means

The grade gets worse while the download runs

A noticeable increase in delay under load suggests that traffic is waiting in a queue somewhere between your device and the internet. This is often called bufferbloat. It can make a video stream feel interrupted even when the download is still transferring plenty of data. Try the congestion fixes below, starting with pausing or limiting the download.

The test stays similar, but the stream still buffers

The download may not be saturating the connection, or the problem may be elsewhere. Weak Wi-Fi, a temporary issue with the streaming service, or a busy device can also interrupt playback. Try watching on a wired connection or closer to the router, and check whether other streams or websites have the same problem.

The connection is slow even when nobody is downloading

This points to a problem that is not limited to traffic from another device. Check your internet speed and test again at a different time. If the connection is consistently slow on several devices, contact your internet provider with the times and results you recorded.

How to fix buffering during downloads

1. Pause the other download. Stop it briefly and see whether the stream recovers. If that fixes playback, the cause is likely congestion rather than a fault in the streaming device.
2. Limit the download speed. Look in the game launcher, cloud sync app, or update settings for a bandwidth limit. Set a lower limit and test the stream again. Keep in mind that a large upload can also slow things down by delaying requests and acknowledgments from your devices.
3. Use a wired connection for the streaming device. If possible, connect the TV or computer to the router with Ethernet. This avoids competition for Wi-Fi airtime, though it cannot fix a connection that is overloaded between the router and your provider.
4. Check which network each device uses. On Windows 11, open Settings › Network & internet › Wi-Fi. On macOS, open System Settings › Wi-Fi. On an iPhone, go to Settings › Wi-Fi. On Android, look under Settings › Network & internet › Internet, though names vary by phone. If your router has separate network names for different Wi-Fi bands, try connecting the streaming device to the less crowded one.
5. Turn on smart queue management if your router supports it. Router settings may call this SQM, Smart Queue Management, or identify a queue method such as CAKE or FQ-CoDel. Start with the router maker's instructions, then rerun the test. A basic priority setting may not help if it does not manage the queue that is causing the delay.
6. Set a realistic bandwidth limit in the router. If SQM asks for upload and download limits, use measured speeds rather than the speed printed on your internet plan. A starting point around 85 to 90 percent of your reliably measured capacity can leave room for queues to stay controlled. Adjust gradually and retest, since the best values depend on your connection.
7. Restart the router and check for updates. Restarting can clear a temporary problem. If the issue returns, check the router maker's instructions for a firmware update and review its queue-management options.

When the router or internet plan may be the limit

If buffering happens on several devices, including one connected by Ethernet, and the Bufferbloat Test grade worsens whenever the connection is busy, the router or internet connection may be the bottleneck. An older router may lack effective queue management, while a slower plan may have too little capacity for simultaneous streaming and downloads.

Retest with one device wired to the router and all other downloads paused. If the wired result is still poor when the connection is busy, ask your internet provider whether your modem or plan is suitable for the load. If only Wi-Fi devices struggle, focus on router placement, wireless interference, or a better access point before changing your internet plan.

The Bufferbloat Test sends test traffic to our server to measure delay under load. It does not need access to your downloaded files.