Stopwatch & Countdown

The stopwatch is driven by the browser’s high-resolution performance.now() clock rather than counting timer ticks, so it measures elapsed time in fractional milliseconds and is not affected by frame-rate drops.

Yes. The remaining time is calculated from the stored end timestamp every time the page updates, so background tabs that throttle timers cannot make the countdown drift or lose time. The remaining seconds are also mirrored into the browser tab title.

It plays a three-tone alarm through the Web Audio API. Because browsers block audio until you interact with the page, press Test sound once to confirm your device volume, and keep the page open until the alarm fires.

Never. Everything runs locally in your browser — no timing data, no account and no server calls. You can safely use the tool on a shared or public computer.