Stopwatch

How to use

1. Start — Press Start to begin timing
2. Lap — Record split times
3. Stop — Pause or reset the timer

What Is an Online Stopwatch?

An online stopwatch is a browser-based timing tool that measures elapsed time with high precision. It mirrors the function of a physical sports stopwatch but adds the convenience of laps, history, and zero hardware to carry. This Zubac Tools stopwatch starts instantly when you press Start and continues counting until you pause or reset, displaying minutes, seconds, and centiseconds for two-digit-millisecond accuracy.

How It Works Under the Hood

The timer uses the browser's requestAnimationFrame API together with performance.now() for monotonically increasing high-resolution timestamps. This avoids the drift problems of setInterval and ensures the displayed time stays accurate even if the tab briefly loses focus on most modern browsers.

Lap Recording Explained

Press Lap while running to capture the current elapsed time as a split. Each lap is added to the top of the list so the most recent split is always visible. Coaches can compare laps to spot pacing changes; runners use them to verify negative splits; presenters track section durations.

Common Use Cases

• Athletics: Time sprints, intervals, and recovery periods
• Cooking: Track multiple stages of a recipe
• Public speaking: Practice talks against a target duration
• Study sessions: Measure focus blocks without a separate Pomodoro app
• Gaming: Speed-run timing and challenge tracking

Tips for Accurate Timing

Keep the browser tab in the foreground — most browsers throttle background timers to save battery, which can pause the visual update (the underlying clock still advances using performance.now, but the display refresh slows). Avoid running heavy scripts in other tabs that share the same process.

Privacy

The stopwatch runs entirely on your device. Lap times exist only in the page's memory and disappear when you close the tab — nothing is uploaded, logged, or shared.

Pair it with the Pomodoro Timer for focused work intervals, the Countdown Timer for deadlines, or the Date Difference Calculator for longer spans.

Frequently asked questions

How accurate is it?

Uses requestAnimationFrame for ~16ms precision. Sufficient for most timing needs.

Can I record laps?

Yes. Press Lap while running to record split times.

Does it work in the background?

Browser tabs may throttle timers in the background. Keep the tab active for accurate timing.

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