Stop your Mac sleeping while you read or watch

You settle into a long article or lean back for a video, and a few minutes in — with your hands nowhere near the trackpad — the screen dims and then goes dark. macOS can't tell the difference between "reading quietly" and "walked away," so after a stretch of no input it sleeps the display. Run caffeinate -d and the screen stays on until you say otherwise, no jiggling the mouse every few minutes.

Keep the screen on while you're still

Reading and watching are the one time you're actively using the Mac while touching nothing. The flag for that is -d, which keeps the display awake regardless of how long you go without a keypress.

# Keep the screen lit until you press Ctrl-C
caffeinate -d

Start it in a Terminal tab, then switch back to Safari, Preview, or your video and enjoy. Nothing dims, nothing locks. When you're finished, return to that tab and press Ctrl-C — your Mac goes straight back to sleeping on its normal schedule, with no setting left changed.

Match it to a movie or an episode

If you know how long you'll be watching, set a timeout so it bows out on its own when the credits roll.

# A two-hour film (7200 seconds), then release
caffeinate -d -t 7200
# A 45-minute episode
caffeinate -d -t 2700

The -t number is seconds: 2700 for 45 minutes, 7200 for two hours. When the timer ends the display is free to sleep again, so you won't accidentally leave the screen burning all evening after you've dozed off.

Why some things already stay awake — and some don't

You may notice full-screen video in Safari, QuickTime, or the TV app usually keeps the screen on by itself: those players tell macOS "I'm playing video, don't dim." The gaps are the passive cases —

• Reading. A long PDF in Preview, an article in a browser tab, an e-book — you're not playing anything, so nothing holds the screen awake and it dims on schedule.
• Windowed or embedded video. Some sites and smaller players don't assert wakefulness unless they're full-screen, so a video in a small window can still let the screen sleep.
• Audio-only. A podcast or album with the lyrics or show notes on screen keeps playing, but the display isn't considered "in use."

In all of these, caffeinate -d fills the gap the app leaves. It's also worth knowing that a screen simply getting dimmer before it sleeps can be automatic brightness reacting to the room rather than sleep kicking in — that's a separate setting, and caffeinate won't touch it.

The Settings route, and why it's blunter

There's no defaults key that maps to this. The nearest thing in System Settings is Lock Screen → Turn display off when inactive, where you can push the delay out to a longer interval or "Never." That works, but it applies to everything, all the time — you'd be keeping the screen awake during genuinely idle periods too, which is worse for battery and burn-in. caffeinate is the surgical version: on for this article, off again the moment you're done.

If it's dimming, not sleeping

When the screen fades but never fully sleeps, the culprit is usually automatic brightness lowering on battery. Our guide to stopping the screen dimming on battery covers that separate switch, which pairs well with keeping the display awake.