Add or subtract hours, minutes and seconds. Find the difference between two times or add a duration to a start time.
Countdown Timer
Count down a set time or to a date and time, with a large full-screen display and alarm.
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Countdown
00:10:00
Set a duration and press Start.
The remaining time is clock-based, but background tabs and sleeping devices can delay the display or alarm. Keep this tab open for important timing.
Runs entirely in your browser. Your files and text are not uploaded.
How to use Countdown Timer
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Step 1: Set a time
Enter a duration, pick a quick preset or switch to a target date and time.
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Step 2: Start the timer
Start, pause or reset the countdown. Allow sound or notifications only if you want them.
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Step 3: Keep it visible
Use full screen for an exam or workout. Keep the tab open for important timing.
A countdown based on the clock
The timer calculates remaining time from the current clock instead of subtracting one second on every display update. That helps it stay accurate when a browser slows a background tab. The display can appear to pause in the background, but it catches up when the browser can run again.
You can count down from a duration or to a specific local date and time. The tab title shows the remaining time while a timer runs. Full screen is useful for workouts, presentations and exams.
Alarm, notifications and screen wake lock
Sound needs a tap or click first, so the browser knows that you chose to start the timer. Notifications are requested only if you press the option, and a wake lock is attempted only while a timer runs. Both depend on browser support and can be switched off by the device.
Browsers can pause pages when the device sleeps, a phone changes apps or the tab is closed. Keep the tab open and the screen on for important timing; do not rely on a browser alarm for safety-critical timing.
Limitations
- Background tabs, sleeping devices and phone browsers can delay or silence the alarm.
- Sound requires a user interaction before it can play.
- Notifications and wake lock depend on your browser permission and device support.
- Keep the tab open and screen on for important timing.
Frequently asked questions
Will the timer stay accurate in a background tab?
The remaining time is calculated from the clock, so it catches up when the browser runs again. The display and alarm can still be delayed while a browser throttles a background tab.
Why did I not hear the alarm?
The tab may be closed, backgrounded, muted or paused by the device. Start a timer with a tap or click and keep the tab open for the most reliable result.
Does this send notifications without asking?
No. A notification permission request appears only when you explicitly choose to enable notifications.
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