How to Keep a Mac From Sleeping: Settings and caffeinate

For good, change System Settings: Lock Screen for the display, Battery → Options… for the Mac itself. For a single task, run caffeinate in Terminal. Neither survives a closed lid unless an external display is connected.

A big download ran for an hour and then stopped. The screen went dark in the middle of a presentation. The build you left overnight is still halfway done in the morning. In all three cases the Mac simply went to sleep on a timer: nobody touched it for a while, so it decided it wasn’t needed. You can change that for good in System Settings, or work around it for one task — for example, with the caffeinate command in Terminal.

First decide what must stay awake — the display or the Mac itself.

The answer tells you which setting to touch.

Display off vs. Mac asleep

These are two different things. When you’re idle, macOS turns the display off first, and the computer itself goes to sleep separately, by its own rules. The screen can be black while the Mac keeps downloading, building and copying: the display sleeps, the system doesn’t.

You need the screen — a presentation, a video, a dashboard you glance at from across the room. Keep the display awake.
You need the work — a download, a backup, a long calculation. Let the screen go dark; keep the system awake.

That’s also the classic mistake: people set the display to Never when all they wanted was a download that doesn’t break — and the laptop lights an empty screen all day.

Built in: for good or for a long while

When the display turns off. System Settings → Lock Screen. On a laptop there are two options: “Turn display off on battery when inactive” and “Turn display off on power adapter when inactive”. On a desktop Mac there’s one: “Turn display off when inactive”. Pick a longer time, or Never.

When the Mac itself sleeps. On a laptop: System Settings → Battery → the Options… button → “Prevent automatic sleeping on power adapter when the display is off”. On a desktop Mac the same option is in Energy and is called “Prevent automatic sleeping when the display is off”.

Note that on a laptop this works only on the power adapter. There’s no built-in setting to stay awake on battery with the display off — and that’s sensible.

The one downside of the built-in route: it’s easy to forget to switch back. For one-off jobs, the temporary options are handier.

For one task: caffeinate

macOS has a built-in command called caffeinate. Open Terminal (Applications → Utilities) and type:

caffeinate — the Mac won’t idle-sleep while the command runs; stop it with ⌃C or by closing the window;
caffeinate -d — keep the display on too;
caffeinate -i <command> — stay awake while a command runs, for example caffeinate -i rsync …; when the command ends, the Mac sleeps normally again;
caffeinate -t 3600 — for an hour (the time is in seconds);
caffeinate -w <PID> — while the process with that number is alive; you’ll find the number in Activity Monitor’s PID column;
caffeinate -s — no system sleep at all, but only on AC power.

Flags combine: caffeinate -d -t 5400 gives you an hour and a half with the screen on — about right for a talk.

The closed lid

Here’s the honest answer: neither caffeinate -i nor apps that keep the Mac from idle sleep survive a closed lid. That’s by design: Apple’s developer documentation says plainly that even with this hold in place the Mac may still sleep when the lid closes, when you choose Sleep from the Apple menu, or when the battery is low.

You can work with the laptop closed if an external display is connected: the Mac carries on using it. For that you need power and an external keyboard with a mouse or trackpad — that’s how Apple describes it too, for example in its article on two displays with an M3 MacBook. Power can come from the adapter or from a display that charges the Mac.

You’ll find pmset commands online that supposedly disable sleep with the lid closed. We don’t give one here: on macOS 27 the key isn’t even in the man pmset manual, and a laptop that stays awake when closed is easy to put in a bag still running. It has no air in there — it heats up and drains to zero.

The opposite problem: the Mac won’t sleep

Sometimes it’s the other way round: you left the Mac, it stayed awake all night, and the battery is empty. Something is holding it. In Terminal:

pmset -g assertions

Under “Listed by owning process” you’ll see who is holding the Mac and why: PreventUserIdleSystemSleep keeps the system awake, PreventUserIdleDisplaySleep keeps the display on. Some apps show a different type, such as NoIdleSleepAssertion — same idea. The short version is the sleep line in pmset -g: after “sleep prevented by”, in parentheses, are the apps responsible.

Without Terminal: Activity Monitor → Energy tab → the Preventing Sleep column. “Yes” means that app is keeping the Mac awake. The rest of the tabs are covered in the guide to Activity Monitor.

Usual suspects: video or music playing in the background, a browser tab with a call, downloads and syncing, file or screen sharing, and a caffeinate forgotten in another Terminal tab.

What not to do

Don’t put the laptop in a bag while something keeps it awake. A closed lid will usually put it to sleep, but if it doesn’t, it will overheat.
Don’t set Never on battery “just this once”: such settings get forgotten, and the charge drains.
Don’t install third-party tools with administrator rights for a single download: the built-in caffeinate is enough.

In the app

In Mac Resources, keeping the Mac awake lives in the menu of its menu bar item: Prevent sleep. Below it:

Display — May turn off (for downloads and builds) or Keep on (for presentations). It’s the same mechanism as caffeinate -i and caffeinate -d;
Duration — 15 minutes, 1, 2, 4 or 8 hours, or Until I turn it off. When time is up, the Mac sleeps normally again;
Turn off when battery is below 20% — on battery, the hold is released automatically and the Mac sleeps normally again instead of draining to zero.

Under the toggle you see the state: Off, On until 18:30, or On until you turn it off. While it’s on, a lock shows in the menu bar item. In pmset -g assertions it’s labeled “Resources Mac: keep awake”.

The toggle doesn’t survive a restart of the app or the Mac, so a hold never lingers unnoticed. The display mode, duration and battery checkbox are remembered. And, just like caffeinate, it doesn’t beat a closed lid: that requires administrator rights, which a sandboxed app doesn’t get. Where the item sits and how to move it is in the guide to the menu bar.

If the Mac stays awake but runs hot and slow, go through the step-by-step diagnosis. And if it’s slow after a macOS update, a night without sleep may be exactly what it needs — see the guide on a Mac slow after an update.