Online Stopwatch
- Start: begin timing
- Pause: suspend timing
- Reset: clear time and laps
- Lap: record current time for split timing
About the Stopwatch
Supports start/pause, reset, and lap records (centisecond precision). Pair with the Keyboard Detector to validate shortcut responsiveness, or cross-check timestamps with the Timestamp Converter.
Uses requestAnimationFrame with performance time source for smooth updates. State persists to local storage and restores after reopen. You can export lap data and inspect it with JSON Formatter.
FAQ
Why not exact milliseconds?
Browser timers and rendering are bounded by system scheduling and refresh rate. We show centiseconds for stable, readable timing.
What happens in background tabs?
Frame rate is throttled. When returning, elapsed time is corrected using the time difference.
How are lap increments computed?
Each lap stores current elapsed time and shows the delta against the previous lap.
Cross-device or multi-window sync?
State is saved per browser window; multiple windows are not synchronized in real time.
Can it continue after refresh?
Yes. While running, start time is saved and restored so timing continues after reload.
Common Use Cases
- Time interval workouts or tasks
- Record lap splits for comparisons
- Measure responsiveness in UI tests
How It Works
- Uses requestAnimationFrame and performance time
- Persists state in local storage for recovery
- Copy and export lap data