Countdown timer

How Countdown Timer works

Dates are computed from your device's clock and timezone settings, both of which stay on the device. Nothing about when you opened the page is reported. Daylight-saving rules come from your browser's own database, so the conversion follows your region rather than a server's guess.

That is the whole architecture: static files, one script, no upload endpoint to leak or log. Close the tab and the work is gone.

Why a timer needs the clock, not a loop

A timer built on setInterval alone drifts: each tick is scheduled after the last one runs, so a busy page loses milliseconds that never come back. Browsers also throttle background tabs, which turns a 25-minute timer into a guess.

This one stores the target moment and recomputes the remaining time from the device clock, so switching tabs, locking the screen or a slow frame cannot shift the deadline.

Built for a room, not a widget

The digits are the largest element on the page and they use tabular numbers, so the layout does not jump as the seconds change. The remaining time is mirrored into the tab title — you can watch it from another app without switching back.

At zero a single 880 Hz tone plays for under a second. That is deliberately short: a repeating alarm is a feature nobody asks for twice.

Nothing to install, nothing to sign up for

Phone timer apps ask for notification permissions and often keep running in the background with an alarm you cannot silence from the page. A tab does exactly one thing: it counts, it shows, it beeps.

The page has no network calls, so it also works on a plane or on a locked-down office network.

Good to know

• Works offline once loaded, including on flights and in locked-down networks.
• No file size limit beyond your device's own memory.
• Free to use, with no account and no usage counter.
• Results are produced locally, so they are not logged or shared with anyone.

Questions