Online Stopwatch Online stopwatch with lap times, start/stop, and reset functionality.

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Stopwatch

Online stopwatch with lap times, start/stop, and reset functionality.

Press Start

Click the Start button to begin timing.

Record Laps

Click Lap to record split times during your activity.

Stop and Review

Stop the timer and review your lap times. Best and worst laps are highlighted.

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What Is Stopwatch?

This online stopwatch provides precise timing with centisecond (1/100th second) accuracy, along with a full lap timing system. Start, stop, and resume timing with simple button controls, and record as many lap splits as you need. The lap table automatically highlights your fastest and slowest laps in green and red respectively, making it easy to analyze your performance. The stopwatch displays hours, minutes, seconds, and centiseconds in a large, easy-to-read format. Each lap shows both the individual lap time (split) and the cumulative total time. The stopwatch uses Date.now() for drift-resistant timing rather than accumulating intervals, ensuring accuracy over long sessions.

Why Use Stopwatch?

Centisecond precision (1/100th of a second)
Unlimited lap recording with best/worst highlighting
Drift-resistant timing using Date.now() references
Clean, distraction-free interface
Works on any device with no installation
Resume capability after pausing

Common Use Cases

Athletic Training

Time sprints, laps around a track, or exercise sets with split tracking.

Cooking

Time cooking processes, marination periods, or baking intervals.

Presentations

Track the duration of presentations or speech practice sessions.

Board Games

Time turns in chess, Scrabble, or other timed board games.

Lab Experiments

Record precise timing for scientific experiments and procedures.

Technical Guide

The stopwatch stores a reference start time using Date.now() when the timer begins, and on each interval tick (every 10ms), it computes elapsed = Date.now() - startRef. This approach is drift-resistant because it doesn't accumulate small errors from setInterval timing jitter. When paused, the current elapsed time is preserved, and on resume, a new startRef is computed as Date.now() - elapsed. Lap times are stored as absolute elapsed timestamps in an array, and individual lap durations are computed as the difference between consecutive entries. The display formatting uses integer division and modulo to break milliseconds into hours, minutes, seconds, and centiseconds.

Tips & Best Practices

1
Use keyboard shortcuts for faster control (Space to start/stop)
2
The best lap is highlighted in green, worst in red
3
Leave the tab open as a background timer — it stays accurate
4
Use laps to time interval training circuits
5
Reset clears both the timer and all recorded laps

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Frequently Asked Questions

Q How precise is the stopwatch?

The display shows centiseconds (1/100th of a second). Internal timing uses Date.now() which has millisecond precision, though display updates every 10ms.

Q Will it lose accuracy over long periods?

No, because it uses absolute time references (Date.now() minus start time) rather than accumulating intervals, it stays accurate over hours or even days.

Q Can I export lap times?

You can copy lap times manually. The lap table shows both individual split times and cumulative totals.

Q Does it work in the background?

The timer continues to run accurately even if you switch tabs, though the display will update when you return.

Q Is there a maximum number of laps?

There is no hard limit on the number of laps you can record. The lap list scrolls to accommodate any number of entries.

Q Can I pause and resume?

Yes, clicking Stop pauses the timer and preserves the current time. Click Resume to continue from where you left off.

About This Tool

Stopwatch is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.