How to use the online alarm clock
- Set the alarm time, add an optional label, choose a sound, and set the volume. Press Test the sound to check that you can hear it.
- To repeat, tick the weekdays under Repeat on. Leave them all unticked and the alarm rings once at the next time that matches.
- Press Start alarm. The page shows when it will ring and how long is left. Keep this page open until it rings.
- When it rings, press Stop, or choose Snooze for 5, 10 or 15 minutes. A repeating alarm sets itself for its next day after you stop it.
When does it ring
It is Thursday, October 15, 2026 at 7:00 AM and you set an alarm for 7:30. It rings today, in 30 minutes. If you set it at 7:30 and 1 second or later, it rings tomorrow at 7:30, because the moment has passed. An alarm for exactly the current minute and second counts as passed too.
With the weekdays Monday to Friday ticked and the time 7:30, an alarm set on Thursday at 8:00 AM rings on Friday at 7:30. Set on Friday at 8:00 AM, it rings on Monday, October 19, because Saturday and Sunday are not ticked. With only Sunday ticked, one set on Saturday afternoon rings on Sunday.
How it works
The page works out the next time that matches your settings and checks the clock every half second. It compares real timestamps rather than counting ticks, so the moment is right even if the page was slowed down for a while. When the time arrives, it plays your sound from your browser, shows a ringing panel and can show a notification if you allowed one.
The sound is generated by your browser, not downloaded, so it works without a connection after the page has loaded. Press Start alarm or Test the sound at least once, because browsers only allow sound after you interact with the page.
Limits you should know about
This is a web page, not a system alarm. It works only while the page is open and the device is awake. A sleeping computer, a locked phone, battery saver modes and tabs that stay in the background for a long time can all delay or stop it, and the notification option depends on your browser and system settings. The page asks the screen to stay awake while it waits, where your browser allows that. Do not use it for anything important, such as a flight, medicine or an exam, and use a second alarm as a backup.
For counting down a set length of time use the online timer, for measuring time use the stopwatch, for work and rest cycles use the Pomodoro timer, and to check the time elsewhere use the world clock.
Assumptions and limits
- Times use your device clock and time zone. If the clock changes for daylight saving time, an alarm for a time that does not exist that day rings at the nearest valid time your browser chooses.
- An alarm rings for up to 5 minutes and is then stopped by the page.
- Your last settings are saved in this browser only, and a running alarm is not saved, so reloading the page cancels it.
- Notifications are only requested after you tick the option, and the wake lock is only requested when you press Start.
Frequently asked questions
How do I set an alarm in my browser?
Pick the time, press Start alarm and keep the page open. It shows when it will ring and plays the sound you chose at that moment.
Will the alarm ring if I close the tab or the computer sleeps?
No. The alarm works only while this page is open and the device is awake. Use a system alarm for anything you cannot afford to miss.
Can the alarm repeat on certain days?
Yes. Tick the weekdays under Repeat on. After you stop the alarm, the page sets it for the next ticked day, as long as the page stays open.
Why do I need to press a button before the sound will work?
Browsers block sound until you interact with the page. Pressing Start alarm or Test the sound unlocks it, so the alarm can play when the time comes.