Stopwatch
Millisecond stopwatch with lap times.
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About the Stopwatch
A millisecond stopwatch driven by requestAnimationFrame for smooth display, showing hours, minutes, seconds and hundredths. Laps record both the split time since the previous lap and the running total, and the timer survives pausing without losing elapsed milliseconds.
How to use the Stopwatch
- Press Start to begin timing.
- Press Lap while running to record a split at any moment.
- Press Pause to stop, then Start again to continue from the same elapsed time.
- Read the Laps box for split and total times, or Reset to clear everything.
Stopwatch FAQ
How precise is the measurement?
It reads performance.now timestamps, which are sub-millisecond, and displays to hundredths of a second โ accurate enough for sports drills and speedruns.
What do the lap columns mean?
Each lap row shows the split duration since the previous lap and the cumulative total at the moment it was pressed, newest lap first.
Does it keep running in a background tab?
Yes โ elapsed time is derived from real timestamps, so switching tabs does not lose time even though the display pauses visually.