Large downloads don't survive sleep
You start downloading a 14 GB macOS update, a 90 GB game from Steam, or a batch of video files from Google Drive. You walk away. Your Mac goes to sleep. When you come back, the download has either paused or failed entirely and you're starting over from scratch.
This happens because macOS turns off the Wi-Fi radio when the system sleeps. Your network connection drops, and the download server on the other end either waits (if you're lucky) or closes the connection. Large files that take hours are especially vulnerable because it only takes one sleep event to ruin the whole thing.
Why your browser won't save you
Some apps request what Apple calls a "sleep assertion," which tells macOS to stay awake while a task is in progress. But plenty of apps don't. Your browser almost certainly doesn't. Safari, Chrome, and Firefox all happily let macOS sleep mid-download. Same goes for the Mac App Store when downloading large updates.
Some apps support resumable downloads, so you can pick up where you left off after waking up. But not all servers support HTTP range requests, and not all apps implement resume correctly. Torrent clients are usually fine since they're built for interruption. A direct HTTP download from a CDN? That's a coin flip.
The fix: Shake It On with the right conditions
Shake It On keeps your Mac awake by moving the mouse slightly at regular intervals. For downloads, there are two conditions you'll want to turn on:
- Paused When on battery. If you unplug your MacBook, shaking stops and your Mac can sleep normally. You don't want a forgotten download draining your battery to zero overnight.
- Only Shake If Wi-Fi connected. Shaking only happens when you actually have a network connection. If your Wi-Fi drops, there's nothing to keep alive, so Shake It On pauses until you're reconnected.
With both conditions enabled, Shake It On keeps your Mac awake while you're plugged in and connected to Wi-Fi. The moment either condition changes, it backs off. You don't have to remember to turn anything on or off.
Pro tip: pair it with Allow display to sleep
If you're leaving a download running overnight, you probably don't need the screen on. Shake It On has an "Allow display to sleep" option that keeps the system awake (so your download continues) while letting the display dim and turn off. Your download keeps running, your screen isn't burning power for no reason, and your Mac sleeps normally once the conditions are no longer met.