Stop background downloads causing lag spikes

A game update, a Windows download or a photo backup can fill your line without anyone noticing, and every game packet and call then waits behind it. The real fix is Smart Queue on your router, which keeps lag low whatever is downloading. These limits help on top of that, or when your router can't do Smart Queue.

Windows updates

Settings → Windows Update → Advanced options → Delivery Optimization → Advanced options. Set a limit for background downloads (a few Mbps, or a percentage of your speed) and for uploads. Turn off "Allow downloads from other PCs", or set it to devices on your local network only, so your PC doesn't upload updates to strangers.

OneDrive

Click the OneDrive cloud icon → Settings → Sync and back up → Advanced settings. Set upload and download to "Adjust automatically", or a fixed rate. Pause syncing while you play or are on a call.

Steam

Steam → Settings → Downloads. Set "Only auto-update games between" to hours you're asleep, and set a download bandwidth limit. Uncheck "Allow downloads during gameplay".

Consoles and other game stores

Let PlayStation, Xbox and Switch install updates in rest or standby mode overnight instead of while you play, and pause downloads from the download queue before a match. On PC, the Epic Games launcher has a download throttle in its settings.

Cloud backups, iCloud and Apple updates

Backup apps upload as fast as your line allows. In Backblaze, use Settings → Performance: lower the number of threads and set a manual throttle. Other backup apps have a similar "limit upload speed" or schedule setting. iPhones and Macs upload photos and download updates mostly while charging overnight; Low Data Mode pauses them.

Mac: spikes every second on Wi-Fi

If a Mac's ping jumps by 50 to 100 ms about once a second on Wi-Fi, it's usually AirDrop's radio link (AWDL) briefly switching channels. Two ways round it:

• Put your router's 5 GHz Wi-Fi on channel 149 or 44. AWDL listens there, so it stops hopping away.
• While gaming, turn AWDL off: sudo ifconfig awdl0 down in Terminal. This stops AirDrop, AirPlay and Sidecar until you run sudo ifconfig awdl0 up or restart; macOS may also turn it back on by itself.

A cable avoids this and every other Wi-Fi spike. The spike finder shows whether your spikes follow this pattern.