Precise stopwatch with lap times and a countdown timer with sound alerts.
00:00:00.00
This is a browser-based stopwatch and countdown timer in one. The stopwatch counts up from zero with millisecond precision and records lap and split times, while the countdown timer counts down from a duration you set in hours, minutes, and seconds and alerts you when it reaches 00:00:00.
It runs entirely in your browser tab, so it works offline once loaded and needs no app install. It is handy for timing workouts and interval training, cooking, presentations and speech rehearsals, exam practice, lab experiments, and any task where you want to measure elapsed time or count down to a deadline.
The tool keeps time using the browser's high-resolution clock rather than a naive counter. On each tick it compares the current timestamp to the moment you pressed Start, so the elapsed value stays accurate even if the browser throttles background tabs or a frame is dropped. Time is displayed as HH:MM:SS.cs, where cs is hundredths of a second (centiseconds).
In stopwatch mode, a lap records the total elapsed time at the instant you press Lap, and the split is the difference between consecutive laps. For example, if lap 1 is recorded at 00:00:45.20 and lap 2 at 00:01:30.50, the second split is 45.30 seconds. In timer mode the remaining time is computed as your set duration minus elapsed time; when the result reaches zero or below, the countdown stops and fires the alert. All timing math happens locally in JavaScript with no server round-trips.
Yes, it is completely free with no sign-up. Everything runs locally in your browser, so your times, laps, and timer settings are never sent to a server or stored anywhere outside your device.
A lap is the total elapsed time captured at the moment you press Lap. A split is the time of one segment only, the difference between one lap and the previous one. The tool shows both so you can compare individual intervals.
Yes. Because timing is based on real timestamps rather than a per-frame counter, the elapsed and remaining values are correct when you return, even if the browser slowed the tab down in the background.
Yes, the timer plays a sound and shows a visual cue when it reaches 00:00:00. Make sure your device is not muted, and note that some browsers require you to interact with the page first before audio can play.
It displays time down to hundredths of a second (centiseconds). This is precise enough for workouts, cooking, and rehearsals, though it is not a certified instrument for official sports timing.
Yes. You can enter hours, minutes, and seconds, so timers spanning several hours work fine as long as the browser tab stays open.
Refreshing or closing the tab resets the tool, since it does not save state to your device. Keep the tab open while a stopwatch or timer is running.