Online Alarm Clock
Set multiple browser alarms with repeat days, snooze, sound, vibration, math dismiss, notifications, timer, stopwatch, and world-clock tools.
Last Updated: July 2026
UTC
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Loading local clock
Next
None
Active
0
Sound
Locked
Alerts
Off
Upcoming
No enabled alarms are scheduled.
Reliability
Keep this browser tab open. Computer sleep, muted system audio, and browser autoplay rules can prevent web alarms from ringing.
Create Alarm
Repeat
No alarms yet
Create a repeating alarm, schedule a one-time date, or use a quick alarm from the live clock panel.
Clock Settings
Browser Notifications
Status: Off
Browser Alarm Reliability
This online alarm clock runs in your browser. It cannot guarantee delivery if the tab is closed, the browser is suspended, the device sleeps, volume is muted, or notifications are blocked. Use a phone or operating-system alarm as a backup for critical reminders.
Checked by Jitendra Kumar
Online Alarm Clock is checked for formula labels, source links, and result limits.
Jitendra Kumar, Founder & Editorial Standards Lead. Updated July 2026. Scope: time calculators.
How to Use This Calculator
Step 1: Enable sound
Press Test sound once so the browser allows Web Audio playback for alarm tones.
Step 2: Create an alarm
Enter a label, select a time, choose repeat days or a one-time date, and save the alarm.
Step 3: Choose alert behavior
Set the alarm sound, snooze length, vibration preference, and optional math-dismiss challenge.
Step 4: Allow notifications
Enable browser notifications if you want a visible alert when the page is open but not focused.
Step 5: Keep the device awake
Use the keep-awake setting where supported, keep the tab open, and avoid letting the device sleep.
Step 6: Use backup for critical alarms
For travel, medication, work attendance, and safety-critical reminders, also set a device-level alarm.
How This Calculator Works
The Online Alarm Clock compares the current local device time against each enabled alarm. Repeating alarms check the selected days of the week. One-time alarms can use a specific date, and quick alarms create a dated alarm for the selected number of minutes from now.
Alarm tones are generated with the browser Web Audio API, so the tool does not need external sound files. Because browsers restrict autoplay, users should press Test sound or save an alarm once before relying on the tone.
Notifications, vibration, and screen wake lock depend on browser and device support. The tool exposes those controls clearly, stores preferences locally, and keeps the alarm list private to the current browser profile.
What to Know Before You Rely on a Browser Alarm
Quick Answer
An online alarm clock is useful when the browser tab stays open and the device remains awake. It is best for desk reminders, study timers, cooking, workouts, meetings, and short focus breaks. It should not be your only alarm for flights, medication, work attendance, or anything safety critical.
| Factor | What matters | Practical guidance |
|---|---|---|
| Best use case | Visible browser tab, active device, enabled sound | Works well for desk reminders, study blocks, cooking timers, meeting nudges, and short naps. |
| Risk to avoid | Computer sleep, closed tab, muted device, blocked autoplay | A browser alarm cannot override every operating-system power or audio setting. |
| Improve reliability | Enable sound, allow notifications, keep the tab open | Use the built-in wake-lock option where supported and test your sound before relying on it. |
| Critical alarms | Use a device-level alarm as backup | For medical, travel, work attendance, or safety-critical wakeups, set a phone or OS alarm too. |
Feature Checklist
| Feature | What it does |
|---|---|
| Multiple alarms | Create separate one-time or repeating alarms with custom labels. |
| Repeat rules | Choose weekdays, weekends, every day, or any custom day mix. |
| Snooze | Set 1, 5, 10, 15, or 30 minute snooze windows. |
| Alarm sounds | Use generated Web Audio tones without downloading sound files. |
| Math dismiss | Require a short arithmetic answer before dismissing selected alarms. |
| Timer and stopwatch | Run countdowns, stopwatch sessions, and lap tracking in the same tool. |
| World clock | Compare local time with major global time zones using Intl time-zone data. |
| Persistence | Saved alarms, snoozes, settings, and world-clock choices persist in this browser. |
Privacy and Storage
Alarms are saved in local browser storage so they survive page refreshes on the same device. CalculatorWallah does not need an account for this tool and does not upload the alarm list. If you clear browser site data or switch devices, you may need to recreate your alarms.
Related Workflows
For work shifts and payroll math, use the Time & Hours Calculator. For global meetings, use the Time Zone Converter. For exact calendar intervals, use the Date Duration Calculator.
Keep the research moving with Time & Hours Calculator, Time to Decimal Calculator, Time Zone Converter, and Date Duration Calculator.
Frequently Asked Questions
Related Calculators
Time & Hours Calculator
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Use Time Zone ConverterDate Duration Calculator
Find exact days, business days, months, years, and calendar intervals.
Use Date Duration CalculatorSources & References
- 1.Time.gov - Official U.S. time(Accessed July 2026)
- 2.NIST Time and Frequency Division(Accessed July 2026)
- 3.MDN Web Docs - Notifications API(Accessed July 2026)
- 4.MDN Web Docs - Web Audio API(Accessed July 2026)
- 5.MDN Web Docs - Screen Wake Lock API(Accessed July 2026)
- 6.MDN Web Docs - Intl.DateTimeFormat(Accessed July 2026)