KOCaffeine: Keeping a Mac Awake, Precisely
A keep-alive utility for macOS with fine-grained control over exactly when the machine stays up.
KOCaffeine stops a Mac going idle. While it is running, the machine will not sleep and the screen saver will not start — useful during a long download, a presentation, a build, or anything that needs to run unattended without someone nudging the trackpad every few minutes.
KOCaffeine on the Mac App Store →
What "going idle" actually means on macOS
Worth understanding, because it is not one thing and that is why a single switch is rarely what people want. macOS distinguishes several states:
- Display sleep — the screen turns off, everything keeps running.
- System sleep — the machine suspends. Network connections drop, work stops.
- Disk sleep — storage spins down or idles.
- Screen saver — separate from display sleep, and separately capable of locking the screen.
These are governed by power assertions: a process tells the system it needs a particular kind of wakefulness, and macOS keeps that state while the assertion is held. Anything that keeps your Mac awake — a video call, a media player, a keep-alive app — is holding one.
Why the granularity matters
A blunt "never sleep" is usually the wrong tool. Downloading a large file overnight needs the system awake but the display can happily turn off and save power. A presentation needs the display awake, and system sleep is not going to happen anyway while you are using it. Leaving a laptop fully awake on battery when only one of those was needed is how you come back to a flat machine.
KOCaffeine exposes the distinction rather than hiding it, so you can say what you actually need and leave the rest to normal power management.
The built-in alternative, and its limits
macOS ships with caffeinate, a command-line tool. caffeinate -d prevents display sleep, -i prevents idle system sleep, -s prevents sleep while on mains power, and -t 3600 sets a duration. You can also wrap a command: caffeinate -i make build holds the assertion for exactly as long as the build runs.
It is genuinely capable, and it is a terminal command with no indication of state, no menu bar presence, and nothing to tell you an hour later whether it is still running. KOCaffeine is the same capability with a UI, which matters mostly for the "did I leave that on?" question.
Checking what is holding your Mac awake
Independent of any app, this is worth knowing: pmset -g assertions lists every active power assertion and the process holding it. When a Mac refuses to sleep and you do not know why, that command names the culprit — frequently a browser tab playing audio, or a file-sync client mid-transfer.
Where it sits
KOCaffeine is distributed through the Mac App Store, so installation and updates are handled by the system and it runs inside the App Store sandbox. Its companion utility Klaar takes the other approach — a direct download — for reasons that come down to what each app needs access to.