Stopwatch Online

Free Online Stopwatch with Lap Timer

This free online stopwatch delivers millisecond-accurate timing with unlimited lap recording, automatic fastest/slowest lap highlighting, and a built-in countdown timer — all in your browser, with no app or download required. Click Start and you’re timing in under a second.

Whether you’re timing a sports drill, tracking Pomodoro work sessions, measuring a presentation, cooking, or running scientific experiments, this stopwatch works on any device — desktop, tablet, or mobile — and stores nothing on our servers. Your timing data stays entirely in your browser.

Stopwatch vs Countdown Timer — Which to Use

The stopwatch counts up from zero and is ideal when you don’t know in advance how long something will take — like timing a race, a workout set, or how long a meeting runs. The countdown timer counts down from a set duration and is best when you want to be alerted when a fixed time period ends, such as a Pomodoro session, cooking a recipe, or a timed exam.

How to Use This Online Stopwatch

1. Start: Click the Start button or press Space to begin timing immediately.
2. Lap: Click Lap (or press L) while running to record a split. The fastest lap highlights green, slowest in red.
3. Pause / Resume: Click Pause to freeze the timer. Click Resume to continue from exactly where you left off — no time is lost.
4. Reset: Stops and returns to zero. Press R as a keyboard shortcut. Laps stay visible until you click Clear Laps.
5. Countdown Timer: Switch to the Countdown tab, enter hours/minutes/seconds or tap a preset, then click Start. A four-beep audio alert plays when it reaches zero.

Timing Accuracy — How It Works

This stopwatch uses the browser’s performance.now() API, which provides sub-millisecond timing resolution — far more accurate than Date.now() which is limited to 1ms precision. The display refreshes every 10ms using requestAnimationFrame, showing hours, minutes, seconds, and milliseconds in real time.

For best accuracy, keep the browser tab active and visible. Some browsers throttle background tabs to save battery, which can cause the display to lag — though the underlying timer remains accurate and catches up when you return to the tab.

Common Uses for an Online Stopwatch

• Sports and fitness: Time 400m sprints, swim laps, rest intervals between sets, or track personal bests across multiple runs using the lap function.
• Pomodoro study sessions: Use the 25-minute countdown preset to work focused, followed by the 5-minute preset for breaks.
• Cooking: Countdown timer with audio alert means you don’t have to watch the screen — just listen for the beep.
• Presentations and speeches: Stopwatch mode lets you track how long you’ve been speaking without being locked to a target time.
• Science experiments: Lap timing is ideal for reaction time tests, chemistry experiments, or any measurement that requires precise split recording.
• Board games and quizzes: Use countdown presets to time turns in games like chess blitz, trivia, or escape room puzzles.

Stopwatch Timing and Browser Throttling

The stopwatch measures elapsed time from the browser clock rather than relying on how often the screen repaints. Background tabs, locked screens, battery-saving modes, and device performance can delay visual updates, but the elapsed result resynchronises when the page becomes active. For laboratory, athletic, or legal timing that requires certified precision, use dedicated timing hardware; this online stopwatch is intended for everyday intervals, workouts, study sessions, and quick checks.

Frequently Asked Questions