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Sleep occurs in cycles of approximately 90 minutes, cycling through light sleep, deep sleep, and REM (rapid eye movement) sleep. Waking up in the middle of a deep sleep cycle causes grogginess — that heavy, disoriented feeling called sleep inertia. The ideal wake-up time falls at the end of a 90-minute cycle, when you're naturally in lighter sleep.
To calculate your optimal wake-up time: count backward from when you need to wake up in 90-minute blocks. If you need to wake at 7:00 AM, ideal bedtimes are 10:00 PM (6 cycles / 9 hours), 11:30 PM (5 cycles / 7.5 hours), or 1:00 AM (4 cycles / 6 hours). While individual sleep needs vary, aligning your alarm with the end of a sleep cycle can dramatically improve how you feel upon waking.
Unlike most online alarm clocks that rely on downloadable audio files, this alarm generates sounds entirely in your browser using the Web Audio API. The API creates sound waves programmatically through oscillator nodes — electronic circuits that produce repeating waveforms. By combining oscillators at different frequencies with gain (volume) envelopes, the API can synthesize everything from simple beeps to complex melodies. This means no audio files to buffer, no external resources to load, and reliable sound output on any modern browser.
Select the hour, minute, and AM/PM for your desired alarm time, add an optional label, choose a tone, and click "+ Add Alarm". Then toggle the alarm on. Keep this browser tab open — the alarm will sound at the set time.
No. Like all browser-based alarm clocks, this requires your computer to be awake and the browser tab to remain open. For critical morning alarms, use your phone's built-in clock app, which works even when the device is locked.
You can, but with the caveat that your computer must stay awake and the browser tab must remain open overnight. We recommend using this online alarm for daytime reminders (meetings, cooking timers, study breaks) and using a phone alarm for morning wake-up calls.
When the alarm sounds, click "Snooze" to silence it for 9 minutes. This mimics the traditional snooze duration found on most physical alarm clocks, which dates back to early mechanical clock designs where adding a 9-minute snooze was the easiest gear modification.
Four tones: Classic (repeating two-tone beep), Gentle (soft chime with slow attack), Urgent (rapid pulse for must-respond reminders), and Melody (ascending four-note sequence). All are synthesized in real-time — no audio files needed.