In its default tray-only mode, Caffeine shows a coffee-pot icon in the Windows notification area. Double-click the icon to switch between keeping the computer awake and temporarily disabling the app. Caffeine, from Zhorn Software, prevents sleep by simulating a key event at regular intervals.
The coffee-pot icon switches Caffeine on and off
When the pot is full, Caffeine is active and sends a simulated key event every 59 seconds to discourage Windows from locking the screen or starting the screen saver. Double-click the icon to empty the pot and pause that behavior; double-click again to reactivate it. The default startup state is active.
The standard event is an F15 key-up signal. If that causes trouble in an application, command-line options can select a different key or use the Shift key. The -keypress option sends a complete key-down and key-up sequence, which may have side effects in some applications.
Command-line switches add timing and activity rules
Caffeine can follow a schedule or respond to conditions instead of staying active continuously. Use -activeperiods with time ranges, -watchwindow to match a window title, or -onac to limit activity to AC power. The -cpu option sets a CPU-usage threshold; the app stays active until usage drops below it.
- -startoff launches in the inactive state.
- -activefor and -inactivefor set timed state changes; -exitafter ends the app after a specified number of minutes.
- -notify shows a notification when the active state changes, and -notwhenlocked makes Caffeine go inactive when the workstation is locked.
Windows can be kept awake without simulated keystrokes
The -stes option tells Windows to stay awake through its execution-state API instead of sending F15. This keeps the computer awake without generating simulated keyboard activity. Add -allowss to let the screen saver start while preventing sleep.
Options such as -showdlg display a status dialog, while -ontaskbar adds a taskbar button for that dialog. Other switches activate, deactivate, or toggle a running instance, so a shortcut or another program can control its state.
Pros
- Double-clicking the coffee-pot icon toggles the awake state
- Command-line options can schedule active and inactive periods
- Can activate only when a matching window title is present
- Offers a Windows execution-state method that does not simulate user input
Cons
- The default F15 event can interfere with PuTTY, PowerPoint, Google Docs, or Smartsheet
System requirements: 32-bit and 64-bit
How do I pause Caffeine?
Double-click the coffee-pot tray icon to empty the pot and make Caffeine inactive. Double-click again to resume.
Can Caffeine keep the PC awake without sending key events?
Yes. Use the -stes command-line option to tell Windows to stay awake through its execution-state API.
Can Caffeine run only during certain hours?
Yes. The -activeperiods option accepts one or more time ranges for when Caffeine should be active.