Online countdown timer that beeps when it’s done

Yes. The countdown is based on the clock, not on the tab being active, and the alarm is scheduled the moment you press start, so it goes off on time from a background tab. When it finishes, the tab title and icon change, the page turns yellow and the sound plays. You can also switch on notifications, so the browser tells you even from a tab you cannot see. The one exception is iPhone and iPad, where Safari stops the sound whenever the page is out of view; the timer tells you so while it runs.

Click the numbers and type the time like on a microwave: 1 0 0 0 gives 10:00, 4 5 gives 00:45, and 1 3 0 gives 01:30. Backspace removes the last digit. Press Enter to start.

Yes. Press the full screen button, or the F key. The numbers fill the screen, which works well on a projector or shared display. Press Esc or the exit button to leave.

Browsers only allow sound after you have clicked something on the page, so press Start rather than reloading a running timer. Check that your device is not muted and that No sound is not selected in the settings bar.

Yes, up to 99 hours. Keep typing digits and the hours appear on the left: 1 3 0 0 0 gives 1:30:00. Or choose 1 hour from the presets.

Yes. The timer runs in any modern mobile browser, and on iOS 18.4 and later it asks to keep the screen awake while it counts down, so the phone does not lock itself mid-timer. Low Power Mode and a low battery will refuse that request, and the timer says so when it happens. Keep the browser open either way: mobile browsers pause audio as soon as you switch to another app.

Add the time to the address, for example beepwhendone.com/#10m, #90s or #1h30m. Open that link and the timer is already set. Share it with a class or a team so everyone starts from the same time.

Yes, and there is nothing to sign up for. No account, no email, no trial and no paid tier. The timer runs entirely in your browser, so there is nothing to install either.

Yes, after the first visit. The page keeps a copy of itself on your device, so it opens and counts down with no connection at all. You will need to be online once to load it the first time, and to pick up any later updates.

Yes, and full screen mode is built for it. Press the full screen button or the F key and the digits fill the display, large enough to read from the back of a room. The bar behind the numbers turns amber as the time runs short, so the class can see how long is left without reading the clock.

Yes. Type 25:00, or open the 25 minute timer to have it set already. The Pomodoro timer runs the work and break periods as one sequence, so you do not have to restart it between rounds.

Nothing about your timer. Your chosen sound, volume and current countdown are stored on your own device so they survive a reload, and none of it is sent anywhere. Visits to the site are counted anonymously, without cookies, and there is no account. The privacy page has the details.