How to use the Countdown Timer & Stopwatch
- Choose Countdown timer or Stopwatch.
- Set a time (or pick a preset) and press Start.
- Pause, reset or record laps; the alarm sounds when the countdown ends.
About this tool
The stopwatch measures time with your device’s high-resolution clock, so it stays accurate even if the display updates slowly. Laps show each split and the running total, with the fastest lap in green and the slowest in red once you have three or more.
The countdown timer keeps correct time if you switch tabs, then plays a beep from your browser (no sound file needed) and flashes the tab title. Try the 25-minute preset for the Pomodoro study technique: 25 minutes of focus, then a 5-minute break. Keep the tab open — closing it stops the timer.
Frequently asked questions
Will the timer still ring if I switch tabs?
Yes, as long as the tab stays open and your volume is up. Some phones pause web pages when the screen locks, so keep the screen on for important alarms.
Why didn’t I hear the alarm?
Browsers allow sound only after you interact with the page — pressing Start does that. Also check the “Alarm sound” box and your device volume.
How accurate is the stopwatch?
It uses performance.now(), accurate to well under a millisecond; the display shows hundredths of a second.