Search for "keep Mac awake" and you get three kinds of answers: a Terminal command called caffeinate, a free menu bar app called Amphetamine, and mouse jigglers. They sound interchangeable. They aren't, and picking the wrong one is why so many people find their Mac wide awake and their Slack dot still yellow.

Two different timers

Your Mac runs two clocks that matter here.

  • The sleep timer. macOS dims the display, then sleeps the display, then may sleep the whole Mac after a period with no input. This is what interrupts downloads, renders and presentations.
  • The idle timer your apps read. Slack, Teams and similar apps ask macOS how long it has been since the last keyboard or mouse input. Past a threshold, they set you to Away. The Mac can be fully awake while this happens.

Keeping the Mac awake only deals with the first clock. Staying Active in your chat apps depends on the second.

caffeinate: built in and free

caffeinate ships with every Mac. Open Terminal and type it, and your Mac stays awake until you press Control-C. The useful flags:

  • caffeinate -d keeps the display on.
  • caffeinate -i stops the Mac from idle sleeping, but lets the display turn off.
  • caffeinate -t 3600 stops after 3,600 seconds (one hour).
  • caffeinate -w 1234 stays awake until the process with ID 1234 finishes, which is handy for a long script or export.

You can combine them: caffeinate -di -t 7200 keeps the screen and the Mac awake for two hours. It costs nothing and installs nothing. The drawbacks are that you need Terminal, it's easy to forget it's running, and it does nothing for your status.

Amphetamine: caffeinate with a menu

Amphetamine is a free app on the Mac App Store that puts the same idea in your menu bar. You start a session for a set time, indefinitely, or while a particular app is running or a download is in progress. It's excellent at what it does, and if all you need is a Mac that doesn't sleep during a long job, it's a great pick.

Like caffeinate, it prevents sleep. It doesn't create keyboard or mouse input, so the idle time your chat apps read keeps climbing.

A mouse jiggler: the one that resets the idle timer

A mouse jiggler, hardware or software, produces small bits of input. Because there is input, both clocks reset: the Mac stays awake and the idle time apps read goes back to zero. That's why it's the only one of the three that keeps a status dot green.

Virtual Mouse Jiggler does this with a tiny, invisible nudge, so it won't drag your cursor across a document. It also adds two things the sleep tools don't: the Away Brief, which shows the notifications that arrived while you were gone, and Insights, which totals how much time it covered.

Which should you use?

  • A long download, backup or export and you don't care about status: caffeinate or Amphetamine. Both are free and both are good.
  • A presentation: caffeinate -d keeps the screen on for the length of the talk.
  • Stepping away while a job runs and you want chat apps to keep showing you as active: a mouse jiggler.

Whatever you use, your company's policies still apply. Keeping a job running is a fine reason to use any of these. Hiding the fact that you're not working isn't one.