How to use the online alarm clock
- Alarm time: pick the time you want it to ring. The line below the fields shows when that will be.
- Snooze length and Message: choose 5, 10 or 15 minutes, and type the text to show when it rings.
- Volume and Test sound: set the loudness and press Test sound once, which also unlocks sound in your browser.
- Press Set alarm, then leave this tab open. Cancel alarm clears it.
- When it rings, press Snooze to hear it again after the snooze length, or Stop to end it. The tab title flashes a bell.
How the alarm works
When you press Set alarm, the tool works out the next moment your device clock shows that time, today if it is still ahead and tomorrow if not, and stores that exact moment. A small background worker checks the clock four times a second, which is meant to keep a hidden tab on time. Browsers block sound until you interact with the page, so the tool starts its audio when you press Set alarm or Test sound. Chrome also slows timers in tabs hidden for more than five minutes, so run a short test alarm before you rely on it.
Worked example
At 10:00 PM, with the defaults (Alarm time 7:00 AM, Snooze length 5 minutes, Message "Time's up!", Volume 70%), the line under the fields reads "Pressing Set alarm will make it ring at 7:00 AM tomorrow, in 9 h 0 min." After you press Set alarm, the status says Alarm set for 7:00 AM tomorrow. Keep this tab open. and the counter shows "Rings in 9 h 0 min". At 7:00 AM the tone sounds, the message "Time's up!" appears, and the button reads Snooze 5 min. Snooze moves the alarm to 7:05 AM.
Limits and edge cases
- The page has to stay open, with the computer awake and the sound on. If the computer sleeps through the time, the alarm rings when it wakes and says when it was due.
- Only one alarm at a time, and it rings once. For daily repeating alarms use your phone's clock app.
- If you reload the page, the alarm is restored, but the browser keeps sound blocked until you click, so press Enable sound.
- An alarm set across a daylight saving change still rings at that time on the wall clock.
- For a count in minutes instead of a clock time, use the countdown timer. To count the days to an event, use countdown to date, and to compare clocks in other cities, use the world clock.
Frequently asked questions
Will the alarm ring if I close the tab or the computer goes to sleep?
No. The alarm lives in the open page, so closing the tab cancels it. If the computer sleeps through the time, the alarm rings when the computer wakes and tells you when it was due.
Why is there no sound when my alarm goes off?
Browsers block sound on a page until you click it. Press Test sound or Set alarm on this page, make sure the tab is not muted, and raise the Volume slider and your device volume. After a reload, press Enable sound.
Can I set more than one alarm or a repeating alarm?
No. This alarm clock holds one alarm at a time and rings once. Set a new one after it rings, or use your phone's clock app for daily repeats.
Can I rely on it to wake me up on my phone?
Not for waking up. Phone browsers often pause a page when the screen locks or you switch apps. Use your phone's own alarm for mornings and this page for short alarms while the screen is on.
What does Snooze do?
Snooze stops the sound and sets the alarm to ring again after the Snooze length you chose, 5, 10 or 15 minutes, with the same message. Stop ends the alarm completely.
Sources: Chrome for Developers, autoplay policy; Chrome for Developers, timer throttling in Chrome 88.