Alarm Clock
Set an alarm for a clock time, with the caveats stated plainly.
No alarm set
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Settings
Clocks here run against real time, so a background tab does not make them drift. Browsers do hold audio in inactive tabs, so a sound may arrive late even when the time is right.
How this calculation works
You set a clock time and the alarm works out the next moment that time occurs, rolling over to tomorrow if it has already passed today. The countdown is measured against the system clock rather than counted down, so a busy machine or a backgrounded tab cannot make it drift. What a browser cannot promise is the sound: audio in an inactive tab is held until the tab becomes visible in most browsers, which is why the limitation is stated here rather than discovered later.
What the results mean
- Rings at
- The exact moment the alarm is set for, including the date. If the time you chose has already passed today, it rolls to tomorrow.
- Time remaining
- Counted from the system clock, so it stays correct while the tab is in the background.
- Armed
- The alarm is active for this tab only. Closing the tab cancels it, and no notification is scheduled anywhere outside the page.
Common problems and fixes
- The alarm did not make a sound
- Use the test sound button first, since browsers block audio until you have interacted with the page. If the test works and the alarm does not, the tab was probably in the background when it fired, and the sound is held until you return. Keeping the tab visible is the only reliable arrangement in a browser.
- The alarm never fired at all
- The device most likely went to sleep, which suspends the page entirely. A laptop closing its lid or a phone locking will stop everything. For anything important, use the alarm built into your operating system or phone, which the system schedules and can wake the device for.
Frequently asked questions
Will the alarm work if I switch to another tab?
The timing will. The sound may be delayed until you come back, because browsers hold audio in inactive tabs to stop pages making noise you did not ask for. The countdown itself is measured against the clock and stays correct throughout.
Does it work if my computer goes to sleep?
No. Sleep suspends the browser and everything in it, and the page has no way to wake the machine. A web page cannot ask a device to wake up, which is the one thing a real alarm clock has to be able to do.
Can I set more than one alarm?
One at a time on this page. Open the page in a second tab for another, though a device that sleeps will lose both. For multiple daily alarms, the operating system alarm application is the right tool.
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