Online Countdown Timer
Set a time, press Start, and get an alarm when it ends. Works in the background and in full screen.
Press Space to start or pause. The screen stays awake while the timer runs, where your browser allows it.
Everything runs in your browser. Nothing you enter is sent to or stored on a server.
How to use the countdown timer
- Pick a quick time such as 5 min, or type hours, minutes and seconds.
- Press Start. The big clock counts down and the time also appears in the browser tab title, so you can see it while you work in another tab.
- When the timer reaches zero it shows "Time's up!" and plays an alarm. Press Stop alarm or Restart to silence it.
Useful features
- Share a preset timer. The address changes as you set the time, for example
?t=1h30mor?t=45s. Use "Copy link to this timer" to send a ready-to-start timer to someone else. - Add time. "+1 min" extends the timer while it is running or after you pause it.
- Full screen. Show the countdown large on a projector or a second screen. The button appears only when your browser supports full screen.
- Keeps the screen awake. While the timer runs the page asks your device not to dim the screen, if the browser supports the Screen Wake Lock feature.
- Warning color. The digits turn orange for the last 10 seconds and red when time is up.
How accurate is it?
The timer does not count ticks. Each time the display updates, it compares the current clock time with the moment the timer is due to end. This means the remaining time stays correct even if the browser slows down background tabs, which browsers such as Chrome do to save power. Hidden tabs may update the display only about once per second, and after several minutes some browsers check even less often, but the alarm time itself is not affected. The display rounds up, so a timer with 0.4 seconds left still shows 00:01.
Tips for reliable alarms
- Browsers only allow sound after you interact with the page. Pressing Start does that, so start the timer yourself instead of loading a link and walking away.
- Check your device volume. On some phones, silent mode also mutes sounds from the browser.
- On a phone, keep the tab open and the screen on for important timers. If the phone locks, the browser may pause the page.
| Format | Meaning |
|---|---|
?t=90 | 90 seconds |
?t=5m | 5 minutes |
?t=1h30m | 1 hour 30 minutes |
?t=1:30:00 | 1 hour 30 minutes |
Frequently asked questions
How do I set a countdown timer?
Choose a quick time or type hours, minutes and seconds, then press Start. You can also open a link such as ?t=10m to load a 10 minute timer and press Start.
Will the timer keep running if I switch to another tab?
Yes. The remaining time is calculated from the clock, not from counting seconds, so it stays correct in the background. The tab title shows the remaining time. If your phone locks the screen the browser may pause the page, so keep the screen on for important timers.
Why did I not hear the alarm?
Check that Sound is on, that your device volume is up and that silent mode is off. Browsers allow sound only after you interact with the page, so press Start yourself rather than relying on a link that loaded earlier.
Can I share a timer with a preset time?
Yes. Set the time, press "Copy link to this timer" and send the link. Whoever opens it will see the same duration ready to start.
What is the longest time I can set?
99 hours, 59 minutes and 59 seconds.
Does this site store anything about me or my timers?
The timers run entirely in your browser. The time you set appears in the page address only so you can share it. See the privacy policy for details about advertising and cookies.