Chronometer — Stopwatch & Countdown Timer
Free online stopwatch and countdown timer with lap tracking, millisecond precision, preset durations, and visual countdown progress bar.
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What Is the Chronometer Tool?
The Chronometer tool combines a precision stopwatch and a countdown timer in a single interface. The stopwatch measures elapsed time with millisecond accuracy and supports lap splits, while the countdown timer lets you set a target duration with quick presets and provides a visual progress bar plus an alert when time expires. Both modes use requestAnimationFrame for smooth, battery-friendly display updates.
How to Use the Chronometer
- Switch between Stopwatch and Countdown using the tabs at the top.
- In Stopwatch mode, click Start to begin timing, Lap to record a split, Pause to halt, and Reset to clear.
- In Countdown mode, enter hours, minutes, and seconds or pick a quick preset (1 min, 5 min, etc.).
- Click Start to begin the countdown. The progress bar fills as time elapses.
- When the countdown reaches zero the display flashes red to alert you.
- Use Pause to temporarily stop and Resume to continue from where you left off.
Common Use Cases
- Performance Benchmarking — Measure how long a manual process or deployment step takes so you can compare optimizations over time.
- Pomodoro & Focus Sessions — Set a 25-minute countdown for focused work intervals followed by short breaks.
- Meeting & Presentation Timing — Use the countdown timer to keep meetings on schedule or time individual presentation segments with laps.
- Debugging & Profiling — Time specific user workflows in a browser or application to identify slow interactions before diving into profiling tools.
FAQ
How accurate is the stopwatch?
The stopwatch uses the browser's performance.now() API and requestAnimationFrame, providing sub-millisecond internal precision. Display updates occur at the screen refresh rate (typically 60 fps), so the visual resolution is approximately 16 ms, while the recorded lap and total times are accurate to the microsecond level.
Does the countdown timer make a sound when it finishes?
The current version provides a visual alert — the display flashes red and shows a 'Time's up!' message. Browser audio autoplay policies vary, so visual feedback ensures reliable notification across all browsers.
Will the timer keep running if I switch tabs?
Yes. The elapsed time is calculated from absolute timestamps (performance.now()), so even if the browser throttles animation frames in a background tab, the displayed time will be correct when you return.