⏰ iAlarmClock

Online Stopwatch

Centisecond precision. Press start, then tap "Lap" to capture splits — best and worst lap are highlighted automatically.

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    How to use the online stopwatch

    1. Tap Start to begin timing.
    2. Tap Lap while running to record a split.
    3. Tap Stop to pause without losing your time.
    4. Tap Reset (the Lap button when paused) to clear and start over.

    What's a "lap" time?

    A lap is the time elapsed between two presses of the Lap button — useful for athletes timing each loop around a track, cooks timing each step of a recipe, or anyone breaking a long task into measurable chunks. iAlarmClock highlights your fastest lap in green and slowest in red so trends pop out at a glance.

    Centisecond precision

    The display updates 100 times a second using requestAnimationFrame, so the readout stays smooth and accurate. Internally we use the browser's high-resolution timer (performance.now()) to avoid drift, even if the tab is briefly throttled.

    Privacy

    Nothing leaves your browser. No accounts, no analytics on your timing. Close the tab and the times are gone.

    Stopwatch FAQ

    Is the stopwatch accurate?
    Yes. We use the browser's high-resolution monotonic timer (performance.now) so timing isn't affected by system clock changes or daylight saving.
    Can I save my lap times?
    Times persist while the page is open. To keep a record, take a screenshot or copy the laps before resetting.
    Does it work offline?
    Yes — once loaded, the page is cached by the service worker and works without an internet connection.
    Will it pause if I switch tabs?
    The clock keeps tracking actual elapsed time even when the tab is in the background, so when you come back the displayed time is correct.