About Stopwatches & Timers
A stopwatch counts upward from zero, letting you measure how long something takes. A timer counts down from a set duration, letting you know when a fixed period of time has passed. Both are everyday tools for sports, cooking, work, study and anything else where precise timing matters.
This tool provides both in one place. The stopwatch runs at millisecond precision using the browser's monotonic clock and includes full lap tracking with split and difference columns. The timer supports presets, custom durations, a progress ring, sound alerts and browser notifications.
Accuracy of a browser-based stopwatch
This stopwatch uses the performance.now() API, which returns a high-resolution timestamp based on a monotonic clock. Unlike the older Date.now(), it is not affected by system clock adjustments (NTP sync, daylight saving changes, manual clock changes), so it never jumps backward or forward unexpectedly.
Real-world accuracy depends on your device:
| Device | Typical accuracy | Notes |
|---|---|---|
| Desktop browser | < 1 ms per hour | Uses system monotonic clock |
| Modern mobile | 1–5 ms per hour | Same; throttled when backgrounded |
| Low-end mobile | 5–20 ms per hour | Depends on clock resolution |
For practical use — sports, cooking, work sessions — this is more accurate than you will ever need.
Lap time, split time and difference
When you press the lap button, three numbers get recorded:
- Lap time — the duration of the segment just completed. This is the time since the previous lap press.
- Split time — the total elapsed time from the start of the stopwatch to the moment of the lap press.
- Difference — how this lap compares to the fastest lap so far. Negative (green) means faster, positive (red) means slower.
The difference column is what makes lap tracking useful. It tells you at a glance which lap was fastest and how much slower each other lap was, without having to compare numbers by hand.
Keyboard shortcuts
| Key | Stopwatch mode | Timer mode |
|---|---|---|
| Space | Start / pause | Start / pause |
| L | Record lap | — |
| R | Reset everything | Reset to set duration |
| Esc | — | Stop and reset |
Keyboard shortcuts work without needing to click any buttons — useful when your hands are occupied with the activity you are timing.
Common presets explained
| Preset | Duration | Common use |
|---|---|---|
| Pomodoro | 25 minutes | Focused work sessions |
| Short break | 5 minutes | Between Pomodoro sessions |
| Long break | 15–30 minutes | After 4 Pomodoros |
| Power nap | 20 minutes | Naps without grogginess |
| HIIT interval | 30–60 seconds | High-intensity training |
| Meditation | 10–20 minutes | Mindfulness sessions |
Common use cases
Sports & fitness
Time runs, intervals, laps and workouts.
Cooking
Timers for baking, steeping, resting.
Study & focus
Pomodoro and timeboxing techniques.
Presentations
Track speaking time without a click.
Experiments
Precise timing for lab or engineering work.
Interval training
HIIT, Tabata, circuit training.
Privacy
This stopwatch and timer runs entirely in your browser. All timing happens locally using standard browser APIs. Nothing is transmitted, stored or logged — your laps and timer sessions are yours alone.