Online stopwatch and countdown timer
The stopwatch measures time to the hundredth of a second, records laps and marks your fastest and slowest. The timer counts down from the duration you set and plays an alarm at zero, with no audio file needed. Both stay accurate even if the browser tab goes to the background.
- ✅ Free
- 🔒 No sign-up
- 📱 Works on mobile
- ⚡ Instant results
🔒 Everything runs in your browser. Your data and files never leave your device.
An accurate stopwatch
The stopwatch reads the browser's high-resolution clock (performance.now) when you start and every time it redraws. It does not count ticks: the time on screen is always the real difference between two readings, so it never drifts, even if the screen refreshes less often.
\[ \text{displayed time} = \text{time accumulated before the pause} + (\text{now} - \text{last start}) \]
Press Lap to record a split: the tool shows the lap time and the total time. The best lap is green and the slowest is red.
A timer with an alarm
Choose hours, minutes and seconds (up to 99 hours) or a quick preset, then start. At zero the browser plays a series of beeps, confetti appears and a phone vibrates if it can. The timer is based on its end time, so it rings on time even from a background tab.
| Use | Typical time |
|---|---|
| Soft-boiled egg | 6 minutes |
| Hard-boiled egg | 10 minutes |
| Pomodoro (work) | 25 minutes |
| Pomodoro (short break) | 5 minutes |
| Study block | 45 minutes |
Reading a time to the hundredth
Hundredths appear after the dot: 01:23.45 means 1 minute, 23 seconds and 45 hundredths. Hours show up after 60 minutes.
| Display | Value |
|---|---|
| 00:09.58 | 9.58 seconds |
| 03:45.00 | 225 seconds |
| 1:02:03.50 | 3,723.5 seconds |
3 real-life examples
A 400 m run in four laps
Press Lap each time you pass the line: 00:21.40, 00:22.10, 00:22.80 and 00:23.50 give a total time of 01:29.80. The first lap is flagged as the best and the last as the slowest.
A Pomodoro session
Tap 25 min, start, and wait for the alarm. Take a 5-minute break with the 5 min button, and repeat four times before a long break.
A hard-boiled egg
Set 0 h 10 min 0 s and start the timer when the water boils. When the alarm rings, exactly 10 minutes have passed, even if you switched tabs.