TimerWorks

Stopwatch

Counts up in hundredths, records laps, and stays accurate whatever else your browser is doing.

00:00

    Reading the clock, not counting frames

    A stopwatch has the same failure mode as a countdown and it is even easier to trip over: if elapsed time is accumulated by adding up intervals, every dropped frame is time that quietly disappears. Under load, or in a background tab, a frame-counting stopwatch can lose whole seconds.

    This one stores the moment you pressed start and subtracts it from the current time. Laps are recorded the same way. The consequence is that the number is right even if the display stutters, which is the correct trade — a stopwatch that renders smoothly but reports the wrong elapsed time is useless.

    Hundredths, and why not thousandths

    The display stops at hundredths of a second deliberately. Browsers deliberately coarsen high-resolution timers to make fingerprinting and timing attacks harder, and human reaction time on a button press is around 200 milliseconds regardless. A stopwatch showing thousandths would be displaying three digits of noise to look precise.

    Other timers

    Countdown timerBookmarkable durations, alarm armed on startInterval / HIITWork and rest rounds, hands-freeHours calculatorTiming billable work? Add up the whole day

    Questions

    How accurate is it?
    It reads the system clock rather than counting frames, so it is as accurate as your device's clock — well within a hundredth of a second over any period you would use a stopwatch for. The display shows hundredths because that is the honest resolution; anything finer would be theatre, since neither your reaction time nor the browser's frame timing supports it.
    Do the laps survive a refresh?
    No. Laps are held in the page only, which is deliberate — a stopwatch is a live instrument, and silently restoring a half-finished session from last week causes more confusion than it saves. Copy the times out if you need to keep them.
    Can I use it for timing work?
    For a single session, yes. If you are timing billable work across a day, the hours calculator in this network is the better tool — it adds up multiple periods, handles breaks and gives you a total you can invoice from.