Overview
Timing things is one of the oldest uses of technology, and the stopwatch remains the honest instrument: it measures what happened, nothing more. This page pairs a precision stopwatch — with lap recording for splits — with a countdown timer that beeps when time runs out. Both run on your device's high-resolution clock, accurate to hundredths of a second.
There is no account, no history uploaded, no permissions asked. The stopwatch is useful for workouts, cooking stages, speeches and experiments; the countdown handles Pomodoro sessions, steeping tea, parking meters and anything else with a deadline.
How precise is a browser stopwatch?
More precise than most people need. The page uses performance.now(), a clock with microsecond resolution that is not affected by changes to your system clock — unlike the wall-clock time shown in your taskbar, which can jump when your computer syncs with a time server. Displayed hundredths are honest measurements, not decoration.
The one caveat is background tabs: browsers slow down timers in tabs you are not looking at, to save battery. For a stopwatch this barely matters, because the elapsed time is computed from the clock, not by counting ticks. For the countdown alarm, keep the tab visible so the beep fires on time.
Features
- Hundredth-second stopwatch driven by a monotonic high-resolution clock.
- Lap recording with newest laps on top and tabular numerals that do not jitter.
- Countdown timer with minute/second inputs and a three-beep WebAudio alarm.
- Pause and resume on both modes without losing elapsed time.
- Tab-switch resilient: elapsed time is clock-derived, not tick-counted.
- Private and offline-capable once the page has loaded.
Benefits
- Zero setup. Open the page and press Start — faster than finding a phone app.
- Two tools, one page. Measure elapsed time or count down, with a tab switch.
- Honest precision. A real monotonic clock, not a ticking estimate.
- No permissions, no noise. Nothing to install, nothing to allow.
Who can use it
Runners and swimmers timing splits, cooks juggling stages, students running Pomodoro sessions, speakers rehearsing to a limit, teachers running classroom activities, and developers benchmarking quick tasks. Anyone who has ever said “give me five minutes” will find the countdown; anyone who has said “how long did that take” will find the stopwatch.
How to use
- Choose Stopwatch or Countdown at the top.
- For the stopwatch: press Start, Lap for splits, Pause to freeze, Reset to clear.
- For the countdown: set minutes and seconds, then press Start — the alarm beeps at zero.
- Keep the tab open while a countdown runs so the alarm fires on time.
- Reset any time to start over; laps clear with the stopwatch reset.
Frequently asked questions
How accurate is the stopwatch really?
To about a hundredth of a second for practical purposes. It reads a monotonic clock that cannot jump when your system time syncs, and elapsed time is computed from timestamps rather than counted ticks, so background-tab slowdowns do not corrupt the measurement. Human reaction time on the buttons (around 150–250 ms) dwarfs any browser error.
Will the countdown alarm work if I switch tabs?
Usually yes, but keep the tab visible to be safe. Browsers throttle background timers to save battery, which can delay the beep by seconds. The stopwatch reading stays correct regardless, because it derives elapsed time from the clock.
Why does the countdown need the tab open?
The alarm is generated live with WebAudio when the timer hits zero. A closed or discarded tab cannot make sound. If you need a guaranteed alarm while working elsewhere, your phone's clock app is the safer choice.
Can I time something longer than an hour?
Yes. The stopwatch display keeps counting minutes past 59 (up to 99 minutes shown as MM), and the underlying measurement has no practical limit. Lap lists scroll if you record many splits.
Is anything recorded or uploaded?
No. Times exist only in the page's memory and vanish on reload. There is no account, no history and no network traffic from the tools.
Conclusion
Two honest instruments: one that measures what happened, one that announces when time is up. Press Start, and trust the clock — it is more precise than your thumb on the button will ever be.