Ping spikes when someone at home uses the internet (Bufferbloat)

Test it first

Measure ping three times: on a quiet line, with the line full of downloads, and with the line full of uploads. If the ping barely moves, downloads at home won't lag your game. If it jumps a lot, games will lag whenever someone uses the line. Note whether downloads or uploads are worse, because the fixes differ a little.

Fix it in the router

The fix that works best is turning on SQM or QoS in the router, if it has it. The router then lets small game packets go ahead of big files. The menu name depends on the brand: look for QoS, SQM or Smart Queue.

Fix it on the PC

• Worse on download: pause Steam, Windows Update and videos while you play.
• Worse on upload (clips, cloud backup, streaming): give those programs an upload limit.
• If the PC has a LAN port but you play on Wi Fi, use a cable. Ping stays steadier, with less lag and warping.
• If ping jumps even on a quiet line, look at loss and jitter too. High loss usually comes from the cable or Wi Fi: restart the router.

Let Savenz Optimizer test it

The Network page of Savenz Optimizer has a Bufferbloat test. It measures ping in all three parts, gives a grade from A+ to F and says whether downloads or uploads are worse. It uses the same kind of data as a speed test site, each part stops after 8 seconds or 400 MB, whichever comes first, and nothing is kept on the PC. The same page has QoS per program, where you can give background programs an upload limit and remove each one again.