How accurate is the stopwatch?

The stopwatch uses performance.now() for timing, which provides sub-millisecond precision in modern browsers. The display updates every 10 ms for smooth millisecond readout.

How do I record lap times?

Click the Lap button while the stopwatch is running. Each lap time is added to the list below, showing both the lap split and the cumulative elapsed time.

What is the countdown timer tab?

The Countdown tab lets you set a specific duration in hours, minutes, and seconds. The timer counts down and shows a completion alert when it reaches zero.

Does it work if I switch browser tabs?

Yes — the timer continues running in the background. When you return, the elapsed time is accurate because it is based on clock differences, not on display refresh cycles.

Can I reset while running?

Yes — click Reset at any time. Resetting a running stopwatch stops it and clears the elapsed time. All lap records are also cleared.

Stopwatch

Precise stopwatch with millisecond accuracy and lap timer. Built-in countdown timer tab. Works even when the tab is in the background.

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How to Stopwatch

Click Start to begin the stopwatch.
Click Lap to record a split time while the stopwatch is running.
Click Stop to pause, then Start again to resume.
Switch to the Countdown tab to set a timer in hours, minutes, and seconds.

Why Use This Tool?

Whether timing workouts, cooking, presentations, or experiments, a reliable stopwatch with lap support is a daily tool. This one works accurately even when you switch browser tabs, using clock-difference timing.

Stopwatch

How to Stopwatch

Why Use This Tool?

Frequently Asked Questions