Stopwatch — Free Online Precision Lap Timer
Track elapsed time with millisecond precision, record laps with split and total times, and run up to three stopwatches simultaneously. Highlight best and worst laps instantly. 100% client-side — nothing leaves your browser.
How to Use the Stopwatch
- Start / Stop — click the Start button or press Space to begin timing. Click again to pause.
- Record a lap — while running, click Lap or press L to capture the current split time.
- Reset — press Reset or R to clear all laps and return to zero.
- Multiple stopwatches — click the + tab to add up to three independent stopwatches.
- Best / worst laps — the fastest lap is highlighted green and the slowest red.
- Export — click CSV or Text to copy your lap data to the clipboard.
Why Use This Stopwatch
Whether you are timing workouts, lab experiments, cooking, or anything in between,
this stopwatch delivers millisecond accuracy using the browser's high-resolution
performance.now() timer. Unlike wall-clock timers, it is not affected
by system clock adjustments.
The lap tracking feature automatically highlights your best and worst splits so you can instantly see where you are improving. Run up to three stopwatches side by side to compare intervals or time multiple events at once.
Frequently Asked Questions
The stopwatch uses performance.now(), which provides microsecond-resolution
timestamps from the browser's monotonic clock. Displayed values are accurate to 1 ms and are
not affected by system clock changes, daylight saving, or NTP synchronization.
The timer continues running in the background. When you return, the display updates immediately. Some browsers may throttle background timers, but the elapsed time calculation remains accurate because it is based on the start timestamp, not accumulated ticks.
The interface supports up to three simultaneous stopwatches for a clean layout. If you need more, you can open this page in multiple browser tabs — each tab runs independently.
Each time you record a lap, the tool compares its split time against all previous laps. The shortest split is marked as best (green) and the longest as worst (red). When a new lap beats the previous best or exceeds the previous worst, the highlights update automatically.
No — lap data is held in memory and is not persisted. When you refresh the page or close the tab, all laps are cleared. This keeps your browsing data private.
Use Cases
Workout Interval Timing
Time workout intervals for HIIT, Tabata, or circuit training with millisecond precision and automatic lap tracking.
Presentation Duration
Measure presentation duration to ensure you stay within time limits and practice delivering talks at the right pace.
Study Session Tracking
Track study sessions using the Pomodoro technique or custom intervals to optimize focus and rest periods.
Code Execution Benchmarking
Benchmark code execution time to measure performance improvements and identify bottlenecks in your applications.
Precise Recipe Timing
Use as a cooking timer for precise recipes that require exact timing for baking, brewing, or molecular gastronomy.