Online Alarm Clock
Set this online alarm clock in seconds: choose the hour and minute, press "Set alarm", and at that time an alarm sound plays until you turn it off or snooze. Quick buttons set the alarm for 10 minutes from now and more.
Source: MDN Web Docs – Web Audio API: AudioContext-Zeitplanung (currentTime, OscillatorNode.start). Updated: .
How it is calculated
How to set the online alarm clock
- Enter the hour (24-hour, 0–23) and minute – for 6:45 pm that is 18 and 45.
- Press "Set alarm". If that time has already passed today, the alarm rings tomorrow; the display shows the day, time and countdown.
- At alarm time a beep sounds every 4 seconds, the device vibrates where supported and the tab title shows an alarm clock. "Snooze" adds 5, 10 or 15 minutes; "Turn off" ends it. After 2 minutes it stops on its own.
For quick reminders, the "in 5 min" to "in 90 min" buttons set the alarm straight away. "Test sound" lets you check the volume first. A label such as "Take the pizza out" is shown in large type when the alarm goes off.
Making sure it rings
- Keep the tab open. The alarm lives in this page; if you close it, nothing rings. After a reload the page restores your alarm.
- Allow sound. Browsers only play audio after you interact with the page – clicking "Set alarm" is enough.
- Avoid sleep mode. While the alarm is set, the page asks the device to keep the screen on (Screen Wake Lock) – this only works in the foreground. No web page can ring while a computer is asleep or a laptop lid is closed.
- Check the volume and make sure the device is not muted.
The alarm sound is scheduled in advance on the browser's audio clock. That clock keeps exact time even in throttled background tabs, so the alarm is on time while you work in another tab.
Alarm clock or timer?
An alarm rings at a time of day (7:30). To ring after a duration (in 12 minutes) with pause and progress bar, use the online timer; to measure time, the stopwatch. Whether your device clock is right shows exact time.
Frequently asked questions
Does the online alarm clock work in a background tab?
Yes. The sound is scheduled on the browser's audio clock when you set the alarm, so it plays on time. You just must not close the tab.
Will it ring when my computer is asleep?
No web page can. While the alarm is set, the page keeps the screen on where the browser allows it; if the device still sleeps, use your phone's alarm as well.
How do I set an alarm for 10 minutes from now?
Tap "in 10 min". The alarm is set at once and rings 10 minutes later.
Can I test the alarm sound?
Yes, "Test sound" plays the beep once so you can adjust the volume beforehand.
How long does the alarm ring?
For two minutes, every 4 seconds. "Snooze" moves it by 5, 10 or 15 minutes, "Turn off" stops it.
Sources and legal basis
- MDN Web Docs – Web Audio API: AudioContext-Zeitplanung (currentTime, OscillatorNode.start)
- MDN Web Docs – Autoplay guide for media and Web Audio APIs
- MDN Web Docs – Screen Wake Lock API
- MDN Web Docs – setTimeout(): Timeouts in inactive tabs
As of:
Related tools
- Online TimerFree online countdown timer: enter any time or tap a 5, 10 or 15 minute preset, get an alarm when time is up, remaining time in the tab. No sign-up.
- Online StopwatchFree online stopwatch with lap times, fastest/slowest lap and copy-to-clipboard. Keeps running after switching tabs or reloading the page.
- Exact time now, with secondsThe exact time now with seconds and tenths – plus how far your device clock is off, measured against our server clock, with round-trip time and error margin.
- Pomodoro TimerPomodoro timer in your browser: 25 min focus, 5 min break, long break after 4 rounds. Free, no sign-up, alarm sound, keeps running in background tabs.
- Countdown to a DateFree countdown to any date: days, hours, minutes and seconds left until your event, live and updating every second – shareable as a link or embed.
- 1 Hour TimerFree 1 hour timer that starts as soon as the page opens, counts down to the second and rings at zero. Full screen and pause, no video ads.