Online alarm clock
Runs in your browser · keep this tab visible
Give it a time of day and press start. It chimes once when your device clock turns that minute, and the live clock above the display shows you the reading it is comparing against.
How to set the alarm
The page reads your device clock four times a second and fires when the hours and minutes match the time you set and the seconds turn over. Everything comes from the machine in front of you, so the alarm inherits whatever that machine believes about the time. A laptop that has been asleep for a fortnight and has not re-synced can sit a minute or two off, and the alarm sits off with it. The live clock exists so you can check it against a watch before you trust it with anything.
Three things stop a browser alarm ringing, and no web page can do anything about any of them. A hidden tab has its timers throttled: down to about once a second at first, and in Chrome to roughly once a minute once the tab has been out of sight for five minutes, at which point the check steps straight over the minute it was waiting for. A sleeping device suspends the browser entirely, so a closed laptop or a locked phone stays quiet. And browsers keep a page silent until somebody has interacted with it, so an alarm can reach its time and make no sound at all. Pressing start yourself settles that last one, since the click counts as the interaction.
What this leaves is a reminder for someone already at the machine: the meeting at half past, the thing in the oven, the call you would otherwise work straight through. For anything you have to get up for, set the alarm on your phone, where the operating system will wake the device to deliver it. One edge worth knowing: the alarm follows the local wall clock, so on the night the clocks go forward an alarm set for 02:30 waits for a minute that never arrives, and on the night they go back it takes the first of the two.
What people use it for
- Catching a meeting that starts at half past while you are heads-down in something else
- Being told when a delivery or a booking window opens without watching the clock
- Ending a study or practice session at a time you decided in advance
- Getting a hard stop on a call from something audible instead of your own willpower
- Marking a market open, a sale start or a ticket drop from a desk you are already at
Questions
No. Closing the tab ends the page and nothing survives it. Leaving the tab open in the background still counts as open.
Sometimes, and worse the longer it stays hidden. Chrome cuts a hidden page down to roughly one timer wake-up a minute after five minutes, and the alarm can miss its minute altogether. Keep it on screen when it matters.
No. A locked or sleeping phone suspends the browser, and no web page can wake a device. Use the phone alarm app for anything you must not miss.
Check that the tab and the system volume are up, and that the mute box is clear. Browsers also keep silent on a page nobody has clicked, though pressing start counts as the click, so an alarm you armed yourself should be allowed to chime.
Your own device clock, read four times a second. The live time above the display is that same reading, so you can hold it against a watch.
One at a time. Entering a new time while it runs replaces the one it was watching for.
No. It chimes once and stops. Set the next time by hand if you want another.
The picker follows your system format, and the value behind it is always 24-hour. Both are the same minute.
Within about a quarter of a second while the tab is visible, since the check runs four times a second.
No. Nothing is stored, so a reload clears the field and you set the time again.
Yes, tick the mute box. The display still switches to Finished at the time you set.
None. The alarm is a chime and a change on the page, so there is no notification prompt and nothing appears outside the tab.
It follows local wall-clock time. On the night the clocks go forward, an alarm at 02:30 waits for a minute that never happens; on the night they go back, 02:30 comes round twice and it takes the first.
Once the page is open, yes. The alarm is a clock check inside your browser and needs nothing from the network to fire.
That is the countdown timer. It measures a length and chimes at zero; this page waits for a moment on the clock.