Countdown Timer

Yes. When you press Start, the timer stores the exact end time and works out the time left from that timestamp several times a second, instead of counting its own ticks. Browsers throttle background tabs, but the maths is based on the clock, so on returning the display is still correct. One exception: if the tab was fully suspended when the countdown ended, the beep may only play once you come back to the tab.

99 hours, 59 minutes and 59 seconds — just under 100 hours. The Hours box accepts 0 to 99 and the Minutes and Seconds boxes 0 to 59, and values outside those ranges are pulled back to the nearest limit as you type. For anything longer than a few hours, bear in mind the timer lives in this browser tab: closing the tab or the browser ends the countdown, and nothing is stored anywhere to resume it later.

Yes, once the page has loaded. The countdown, the display and the finishing beep are all generated by your browser — no part of the timer talks to a server while it runs, so you can switch off Wi-Fi or mobile data and it will keep counting and still beep at zero. You only need a connection to load or reload the page itself; reloading also resets the timer back to the values in the boxes.

No. This timer does not use the notifications system and never asks for permission to send alerts, so it cannot pop up over other apps or wake a sleeping screen. The finish signal is the beep plus the Time's up! message on the page itself, and the tab title shows the time left while it runs. If your device is asleep or the tab is suspended at zero, the beep may wait until you return to the tab.

So you can keep working in other tabs without losing track of the countdown: while the timer runs, the tab title shows the remaining time in HH:MM:SS and updates as it counts down, exactly like glancing at the page itself. The moment you press Pause or Reset, or the countdown reaches zero, your original tab title is restored — nothing about the title change is permanent, and leaving the page restores it too.

As accurate as your device's own clock. The end time is a real timestamp, and the remaining time is recalculated from it about five times a second, so the small delays browsers impose on background tabs cannot build up into drift the way they do with timers that simply count down one second at a time. If your phone or computer clock is a few seconds out, the timer finishes a few seconds out by the same amount.

No. The timer runs entirely on this page in your browser — there is no account, no download and no app to install, and the time you set is never sent anywhere or saved. That also means there is nothing to sync between devices: each tab runs its own independent countdown, so you can open the page in two tabs and run two different timers side by side if you need to.