Online Alarm Clock
Clean, simple web alarm clock with custom wake sounds, snooze button, and quick presets.
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Important Reliability Note
This online alarm depends on your browser and device remaining active to run the page. Device sleep, computer shutdown, tab suspension, or aggressive OS power-saving modes may prevent the alarm sound from playing. For critical morning wake-ups, always use your smartphone or native device hardware alarm.
How to Use the Online Alarm Clock
Choose your target hour and minute using the digital time picker, or click any quick preset chip (+5m, +15m, +30m, +1h) to advance from the current time.
Open Settings to pick your wake tone (Chime, Bell, Digital Beep, or Gentle chime) and enable Keep Screen Awake to prevent display sleep.
Click "Set Alarm". Keep your device on and browser tab open. When the alarm triggers, click "Snooze (5m)" or "Stop Alarm".
Alarm Clock Features
Wall-Clock Drift Free
Synchronized with authoritative local system timestamps rather than simple counters, ensuring exact scheduled trigger time.
Procedural Audio Alerts
Synthesizes clean offline sound tones using the Web Audio API without relying on external media files.
Distraction-Free Fullscreen
Press F to expand to a large-digit nightstand display visible across bedrooms, classrooms, or offices.
Screen Wake Lock API
Prevents supported device screens from dimming or locking while an alarm is actively scheduled.
Frequently Asked Questions
How does this online alarm clock calculate target times?
The alarm uses your device local timezone and authoritative wall-clock timestamps (Date.now()). If you set an alarm for a time that has already passed today, it automatically and safely schedules for that time tomorrow using calendar calculations.
Will the alarm sound play if my computer goes to sleep or is turned off?
No. Like all web browser applications, this page requires an active browser session to execute JavaScript and play sound. Device sleep, computer shutdown, or OS power-saving suspension will prevent the alarm from sounding. For vital wake-ups, always use your smartphone or native device hardware alarm.
Can I keep the screen awake while waiting for the alarm?
Yes. You can enable "Keep screen awake" in Settings. When supported by your browser, it utilizes the Screen Wake Lock API to prevent your display from dimming while the page is active.
How does the Snooze feature work?
Clicking "Snooze 5 Min" when the alarm rings immediately silences the sound and schedules a new alarm for exactly 5 minutes from the current moment.
Can I set an alarm using keyboard shortcuts or shareable links?
Yes. Press Space to set or stop the alarm, and F to enter Fullscreen mode. You can also share or bookmark custom alarm times (for example, freetimertools.com/alarm-clock/?time=07:30).
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