Online Alarm Clock

Set a time, leave the tab open

The clock at the top is the current time on your own device, running live. Below it you choose the time to ring at and, if you want, a label. Press set and the page tells you how long is left and shows the time it is counting to.

A time that has already gone today rolls over to tomorrow, which is what every alarm clock ever built does, and what someone setting 07:00 at midnight means. When the moment arrives the clock turns vermilion, the label appears, and the alert repeats every three seconds until you dismiss it. Snooze pushes it five minutes and starts counting again.

The honest limitation

This is a browser alarm, and a browser alarm needs its page open to ring. If you close the tab there is nothing left running to make a sound. No web page can get around this, and any page that implies otherwise is either about to ask for notification permission or is not being straight with you.

So: for anything with a consequence, a flight, a medication, a meeting you cannot be late to, use the alarm on your phone. This page is for the alarms that live on a desk. You are at a computer, you need telling at a particular time, and setting it here is faster than reaching for a phone and unlocking it.

Within that, it is built to be dependable. The alarm is saved in your own browser, so an accidental refresh, a crash or a closed and reopened tab does not lose it. It keeps correct time in a background tab, because the countdown runs from a deadline on your system clock rather than being counted while the page is watched. And an alarm whose time passed while the page was closed is quietly discarded rather than ringing at you for something four hours old.

Sound, and why it has to be armed

Browsers will not play audio that no interaction asked for. It is a good rule, and it creates a specific problem for alarms: at the moment the alarm should sound, there has been no interaction for hours.

The way round it is to prepare the sound while your click still counts. Pressing set arms the audio, and from then on the alarm can ring without needing anything from you. The practical consequence is small but worth knowing: set the alarm by pressing the button rather than expecting it to arm itself, and it will sound.

It repeats every three seconds rather than playing once, because an alarm you slept through is not an alarm. It stops after three minutes on its own, so a forgotten tab in a window behind everything else does not ring at an empty room for an hour.

What people use a desk alarm for

Not usually waking up. The common uses are the ones where you are already at the computer and would otherwise lose track: leaving in time for something, joining a call, taking something out of the oven, moving a car before a parking restriction starts, ending a work session at a fixed time rather than when you run out.

The label matters more than it looks for exactly that reason. An alarm that says only that it is four o'clock is a puzzle by the time it goes off. An alarm that says "leave for the station" is an instruction.

The other way of asking the same question

An alarm is set to a time of day. A timer is set to a length. They answer the same need from opposite ends, and picking the wrong one makes you do arithmetic you did not need to do.

If you know you want twenty minutes from now, use the timer rather than working out what time that is. If the thing is a date rather than a time today, the countdown handles days and can be shared as a link. If you want to be told repeatedly on a cycle, the pomodoro timer or the interval timer will run the pattern for you rather than making you set an alarm each time.