Countdown Timer

What is Countdown Timer?

Countdown Timer is an online tool for setting countdowns for specific time periods. Supports custom hours, minutes, seconds with automatic alerts (sound + visual) when time's up. Uses localStorage to save settings, precision ±10ms. Suitable for Pomodoro technique, exam timing, and cooking timers.

How to Use

  1. Set hours, minutes, seconds
  2. Click start button
  3. View real-time countdown
  4. Automatic alert when time's up

Features

  • Supports up to 99 hours 59 minutes 59 seconds
  • Precision ±10ms
  • Supports browser notifications and sound alerts
  • Automatically saves settings

FAQ

What is Countdown Timer?

Countdown Timer is an online tool for setting countdowns for specific time periods. Supports custom hours, minutes, seconds with automatic alerts (sound + visual) when time's up. Uses localStorage to save settings, precision ±10ms.

What time range is supported?

Supports any combination of 0-99 hours, 0-59 minutes, 0-59 seconds. Maximum 99 hours 59 minutes 59 seconds (about 4 days). Minimum 1 second. Custom presets supported (e.g., 25-minute Pomodoro).

Does it alert when countdown ends?

Yes. Supports two alert methods: (1) Browser notifications (Notification API); (2) Sound alerts (Web Audio API). Requires user permission for notifications. Both methods can be enabled simultaneously.

Are settings saved?

Yes. Uses localStorage API to save countdown settings, automatically restores after page refresh. Supports saving multiple preset times. Clearing browser data will delete saved settings.

How precise is it?

Precision ±10ms. Uses requestAnimationFrame method for real-time display refresh, more accurate than setInterval. Based on system clock calculation, unaffected by page performance.

What are the use cases?

Suitable for: (1) Pomodoro technique (25-minute focus); (2) Exam timing; (3) Cooking timers; (4) Sports interval training; (5) Meeting time control. Supports running multiple countdowns simultaneously.

Is data uploaded to servers?

No. All timing is done locally in the browser using native JavaScript Date object and Performance API. No internet connection required, protecting privacy.

Does it work on mobile?

Fully supported. Responsive design adapts to phones, tablets, and computers. Works on iOS Safari 12+, Android Chrome 80+. Supports background running (continues timing when page is minimized).