How to use the countdown timer
- Type the hours, minutes and seconds; 90 minutes works as well as 1 hour 30. Blank boxes count as 0.
- Start counts down and shows the clock time it will end; the same button then says Pause. Reset goes back to the time in the boxes.
- When it reaches zero you see Time’s up, the browser tab says so too, and it beeps unless you turn the beep off. It only ever makes a sound after you have pressed Start.
- The link carries the time you set, so a bookmark or a shared link opens the same timer, ready to start.
Quick timers
Each of these opens the timer set and ready to start:
Does the timer keep going in another tab?
Yes. Browsers slow a page’s timers down when it is in the background, so a timer that counted its own ticks would finish late. This one works out the moment it will end when you press Start and checks your device’s clock against it, so it ends on time wherever you are. The beep is scheduled with your browser’s sound clock at the same moment, so it sounds on time too.
Source WHATWG · HTML Standard, Timers ↗
FAQs
How to add a countdown timer in PowerPoint?
PowerPoint has no timer button, but you can animate numbers to disappear one second apart: add text boxes 5, 4, 3, 2, 1, give each a Disappear exit animation, start the first On Click with a 1-second delay and the rest After Previous, each with a 1-second delay. Or keep this page open beside your slides.