Overview
The stopwatch is the honest instrument: it measures what happened and editorialises nothing. This page pairs one — with lap recording for splits — against a countdown timer that sounds an alarm at zero. Both read your device's high-resolution clock, so the hundredths on screen are measurements, not decoration.
No accounts, no history, no permissions. The stopwatch serves workouts, speeches, cooking stages and experiments; the countdown covers Pomodoro sessions, steeping tea, parking meters and every other deadline with a beep at the end.
How precise can a browser timer be?
Surprisingly precise. The page reads performance.now(), a monotonic clock with microsecond resolution that never jumps when your system syncs its wall-clock time. Elapsed time is computed from timestamps rather than counted ticks, so even if the browser throttles background tabs, the measurement stays correct.
The practical limit is your thumb: human reaction time on start/stop is around 150–250 milliseconds, dwarfing any browser error. For the countdown alarm, one caveat — keep the tab visible so the beep fires on schedule, since background tabs get deprioritised.
Features
- Hundredth-second stopwatch on a monotonic high-resolution clock.
- Lap capture with newest splits on top and jitter-free tabular numerals.
- Countdown with alarm: set minutes and seconds, get a triple beep at zero.
- Pause and resume on both instruments without losing time.
- Clock-derived elapsed time, immune to background-tab throttling.
- WebAudio alarm generated live — no audio files needed.
- Minimal chrome: big readable digits, three buttons per mode.
- Private and offline-ready once the page loads.
Benefits
- Faster than any app. Open the page, press Start — no install, no permissions.
- Two tools, one tab. Measure elapsed time or count down, one switch apart.
- Trustworthy digits. A real monotonic clock behind the display.
- Silent about you. Times exist only in the page's memory.
Who can use it
Runners logging splits, swimmers timing sets, cooks staging dishes, students running Pomodoro blocks, speakers rehearsing against a limit, teachers running timed classroom drills, and developers casually benchmarking tasks. If you've ever said “time me” or “give me five minutes”, one of the two modes is yours.
How to use
- Pick Stopwatch or Countdown at the top of the tool.
- Stopwatch: Start to begin, Lap for splits, Pause to freeze, Reset to clear.
- Countdown: enter minutes and seconds, press Start — the alarm beeps at zero.
- Keep the tab open during a countdown so the alarm fires on time.
- Reset either mode any time to start fresh; laps clear with the stopwatch.
Frequently asked questions
How accurate is the stopwatch?
To about a hundredth of a second for any practical purpose. It reads a monotonic clock that can't jump during time syncs, and derives elapsed time from timestamps instead of counting ticks, so throttled background tabs don't corrupt it. Your reaction time pressing the buttons is a hundred times larger than any browser error.
Will the alarm sound if I switch tabs?
Usually, but keep the tab visible to be certain. Browsers slow background timers to save battery, which can delay the beep. The stopwatch reading stays exact regardless — only the alarm's punctuality is at stake.
Why must the tab stay open for the countdown?
Because the beep is synthesised live with WebAudio at the moment the timer hits zero. A closed or discarded tab can't produce sound. For alarms you must not miss while working elsewhere, a phone's clock app remains the safer bet.
Can it time things longer than an hour?
Yes — minutes keep counting past 59 and the underlying measurement has no practical ceiling. The lap list scrolls if you record a great many splits.
Are my times recorded anywhere?
No. Laps and totals live in the page's memory until you reset or leave. There is no account, no history file and no network traffic from either tool.
Conclusion
Two instruments, zero ceremony: one that tells you how long something took, one that tells you when time is up. Press Start and trust the clock — it's steadier than the thumb pressing the button.