Display sleep vs. system sleep
macOS has two separate sleep stages. Most people don't realize they're different.
Display sleep turns off the screen. Mac keeps running. Downloads continue, music plays, background tasks keep going. Just the screen goes dark.
System sleep shuts everything down. CPU idles, network drops, processes freeze until you wake it.
When someone says "my Mac keeps going dark," they almost always mean display sleep. The system is still awake, the screen just turned off. Different problem, different fix.
Why your screen dims and goes dark
System Settings → Energy Saver (desktops) or Battery → Options (laptops). "Turn display off after" slider. This controls how long macOS waits after your last mouse or keyboard input before dimming.
Default is usually 2-5 minutes on battery, 10-15 on power. Before the screen fully turns off, macOS dims it as a warning. Move the mouse during the dim and it cancels.
You can drag it to "Never," but then your screen literally never turns off on its own. Laptop battery drains faster. Desktop display stays lit indefinitely when you walk away. Neither is ideal.
Keep the screen on with Shake It On
Shake It On moves your mouse at regular intervals. Each movement resets the idle timer, so macOS never starts the dimming countdown. Screen stays on as long as your conditions are active.
Better than changing Energy Saver because it's conditional:
- Screen on only when plugged into power
- Screen on while a specific app is running
- Screen on during work hours, dims at night
- Pause when the camera is in use (video calls unaffected)
When none of your conditions are active, Shake It On does nothing. Normal display timeout kicks in. Screen on when you need it, off when you don't.
When you want the screen off but the system awake
Sometimes you want the opposite. Mac running, screen dark. Overnight download, server process in a dark room, that kind of thing.
Shake It On has an "Allow display to sleep" toggle for this. Prevents system sleep (Mac keeps running, network stays up) but lets the display dim and turn off on its normal schedule. Downloads finish, processes run, screen stays dark.
Hard to do with Energy Saver alone. The built-in settings tie display and system sleep together in ways that are tough to untangle. Shake It On gives you independent control over each.