Amphetamine

Every Mac gets a keep-awake app eventually, usually the day a long upload dies because the screen locked. Amphetamine is the one that grew a brain. Instead of a toggle you get triggers: stay awake while Handbrake is running, while this external drive is mounted, while I am on the office Wi-Fi, or while the CPU is above a threshold you set. Sessions can run on a timer, keep the display off while the machine carries on working, or survive a closed lid on hardware that permits it.

It is free on the Mac App Store and the developer is blunt about why: no in-app purchases, nothing to unlock, no pro version, and that has held for over a decade.

The cost is elsewhere. App Store distribution means no licence file and no installer to keep. The preferences window is genuinely dense — the trigger system rewards half an hour of reading and punishes skimming. Closed-lid operation depends on power and an external display on most Macs, which is Apple's rule, not the app's. And it is closed source, so you are trusting the no-tracking statement.

If all you ever need is to keep the machine up during one long task, caffeinate -d is already installed and costs nothing to learn.