This countdown timer alerts you when a specified duration has elapsed. Set the hours, minutes, and seconds, then click Start. A progress bar visualises the remaining time, and an audio alert plays when the timer reaches zero.
Formula Used
Time Remaining = Target End Time − Current Timestamp
Target End Time
— the absolute timestamp when the countdown should end
Current Timestamp
— the system clock timestamp at the current frame
Time Remaining
— the difference in seconds, formatted as HH:MM:SS
Example Calculation
If you set a timer for 5 minutes, the target duration is 300 seconds. The countdown progresses, and when remaining time reaches 0, the browser triggers the alarm sound.
Frequently Asked Questions
Yes. The timer calculates remaining time using the system's absolute clock, ensuring it remains accurate even if the browser tab is minimised or goes to sleep.
Yes. Clicking 'Pause' halts the countdown. Clicking 'Resume' recalculates a new target end time based on the remaining seconds, letting the countdown continue.
No. The alert relies on the browser's audio API. If your device volume is muted or your browser has blocked autoplay audio, the alarm will not be audible, though the visual alert will still flash.
This simple timer tool supports one active countdown at a time. If you need multiple timers, you can open additional tabs of this page in your browser.
Click 'Reset' or 'Cancel' to stop the active countdown, reset the progress bar, and return the inputs to their default states.