Online Stopwatch

It uses your browser's high-resolution performance timer, accurate to hundredths of a second. Elapsed time is always recomputed from timestamps rather than counted tick by tick, so display lag never accumulates as error.

Yes. Because elapsed time is derived from clock timestamps, backgrounding the tab or a laggy frame rate does not affect the measured time — when you come back, the display is still correct.

Click Lap (or press L) while the stopwatch runs. Each lap shows its own split time and the total elapsed time, with the fastest and slowest laps highlighted in green and red.

A stopwatch counts up from zero to measure how long something takes. A timer (or countdown) starts at a set duration and counts down to zero. For counting down, use a countdown timer instead.