How to use the countdown
- Choose To a date and pick a date and time, or For a duration and type how long: 10 (minutes), 1:30 (a minute and a half), 1h 30m, 90s.
- Give it a title if you like. It is shown above the numbers and in the browser tab.
- Press Start. The browser tab title shows the time left, so you can see it while working in another tab.
- At zero, the page plays a short tone and shows "Time is up!". Press Enable notification first if you also want a system notification when the tab is hidden.
- Press Copy link to share the countdown. Anyone opening a link to a date sees the same countdown running on their own clock.
Why it stays accurate
A simple timer subtracts one second every second. That goes wrong quickly in a browser: to save battery, browsers slow down timers in tabs you are not looking at, sometimes to once a minute, and a laptop that sleeps stops them entirely. After a lunch break such a timer can be many minutes off.
This countdown never counts down. It stores the moment it should end and, whenever it redraws, computes the remaining time as that moment minus the current time. However long the tab was in the background, the first redraw afterwards is correct. Seconds are rounded up, so the display reaches 00 exactly when the time runs out rather than a second early.
Dates and time zones
A date countdown uses the date and time as your device understands it, in your time zone. A shared link contains that local date and time, so someone in another time zone counts down to the same clock time where they are — useful for "midnight on New Year's Eve", less so for a live event at one fixed moment. For fixed events, share the time in the event's own time zone, and use the time zone converter to translate it.
Sound and notifications
Browsers only allow a page to play sound after you interact with it, so the tone is enabled when you press Start. The tone is generated in the page with the Web Audio API — there is no audio file to download. Notifications need your permission, requested only when you press the button; they appear even if the tab is in the background.
Examples
| Input | Meaning |
|---|---|
25 | 25 minutes |
1:30 | 1 minute 30 seconds |
1:02:03 | 1 hour 2 minutes 3 seconds |
1h30m | 90 minutes |
1.5h | 90 minutes |
90s | 90 seconds |
Counting down from 12:00 UTC on 28 September 2026 to midnight UTC on 1 January 2027 shows 94 days and 12 hours. A remaining time of 90,061 seconds displays as 1 day, 1 hour, 1 minute and 1 second.
Shared links look like this: /countdown-timer/?to=2026-12-31T23:59:59&title=New+Year for a date, or /countdown-timer/?d=25m&title=Tea for a duration. Date links start counting as soon as they open; duration links wait for Start.
Limits
- The page must stay open. Closing the tab stops the countdown and its alert. Sleeping devices do not wake up to sound an alarm; the countdown is correct again once they wake.
- Muted or silent devices will not play the tone, and some mobile browsers do not show notifications from ordinary web pages.
- Your device clock is the reference. If it is wrong, the countdown is wrong by the same amount.
- One countdown per tab. Open another tab for a second timer.
Frequently asked questions
Will the countdown keep running if I switch tabs?
Yes, and it stays accurate, because the remaining time is always calculated from the end time and the current clock rather than by counting ticks.
Can I share a countdown?
Yes. Copy link puts the date or duration and the title in the address. A date countdown starts automatically for whoever opens it.
Why did I not hear the alarm?
Check that the device is not muted and that the page was not closed. Browsers only allow sound after you have pressed a button on the page, which Start does.
How do I get a notification when the tab is hidden?
Press Enable notification and allow notifications when the browser asks. You can withdraw the permission in your browser settings at any time.
Is anything stored?
No. The countdown lives in the page and in its address; nothing is saved in your browser or sent to a server.