Online Stopwatch

The stopwatch uses JavaScript's Date.now() for high-resolution timing and updates every 10ms. It's accurate to centiseconds (hundredths of a second). For precision timing, note that browser background tabs may throttle timers.

The stopwatch uses absolute timestamps (not interval counting), so time stays accurate even when switching tabs. When you return, the display catches up to the actual elapsed time.

The stopwatch uses absolute timestamps (Date.now()), so if your computer sleeps and wakes up, the timer will show the correct elapsed time including the sleep period. A brief display freeze may occur during wake-up as the display catches up, but accuracy is restored automatically.

The tool provides a single stopwatch per page. For multiple independent timers, open the page in multiple browser tabs and run each independently. Each tab has its own stopwatch instance with separate start/pause/lap controls that don't interfere with each other.

JavaScript's Date.now() returns milliseconds since Unix epoch, supporting durations up to roughly 285,000 years. For practical use, the stopwatch can run indefinitely — days, weeks, or longer. The display handles any duration, rolling over from 99:59:59 to 100+:00:00 correctly for extended timing sessions.

Lap times are displayed in a scrollable list below the timer. You can manually copy them or take a screenshot. There's no built-in export, but the data is visible and accessible in the UI.