How accurate is an online stopwatch?
This stopwatch uses the browser's high-resolution timer (requestAnimationFrame), which is accurate to within a few milliseconds — more than precise enough for workouts, cooking, study sessions, or sports training. For official athletic timing, dedicated hardware stopwatches or photo-finish systems are still used, since human reaction time when starting/stopping (150–300 ms) is the larger source of error in any manually-triggered stopwatch.
What is a lap time and how is it useful?
A lap time records the elapsed time at a specific moment without stopping the overall stopwatch — useful for tracking interval splits during a run, comparing rounds in a workout, or timing repeated tasks. This stopwatch highlights your fastest lap in green and slowest in red once you have recorded more than one, making it easy to spot pacing trends.
Can I use a stopwatch for interval training (HIIT)?
Yes, though a dedicated countdown timer with audible alerts (like our Countdown Timer) is often more convenient for fixed work/rest intervals since it counts down to zero automatically. A stopwatch is better suited for open-ended timing — e.g. "how long did that set take" — or for recording lap splits across multiple rounds of a circuit.
Does the stopwatch keep running if I switch browser tabs?
Yes — the timer is based on actual elapsed wall-clock time (calculated from timestamps), not a simple counter that could drift or pause when the tab loses focus, so the displayed time remains accurate when you return to the tab.
Why is a hand-timed result always slightly off?
Because your reaction time is inside the measurement. Human reaction to a visual cue is roughly 200 to 250 milliseconds, and it applies at both start and stop — partly cancelling out, but not reliably. This is why hand-timed sprint results have historically been adjusted before comparison with electronic times, and why hundredths of a second on a manual stopwatch imply a precision that is not really there. For anything where a tenth matters, the timing has to be triggered by the event rather than by a person watching it.
Can I use this for official race timing?
No. Sanctioned competition requires certified timing equipment, usually triggered electronically by the starting signal and by a beam or transponder at the finish, along with calibration records and defined procedures. A browser stopwatch is entirely adequate for training intervals, cooking, presentations and personal bests, where a fraction of a second changes nothing. It is not adequate where a result is recorded, ranked or appealed — and any governing body will specify what it does accept.