Countdown Timer

Choose a length, give it a name if you like, and start. The clock runs inside the page, so nothing you type leaves your device.

1. Pick a Quick start such as 5 minutes, 25 minutes or 1 hour. It fills the three time fields for you. Leave it on Custom time if you prefer to type.
2. Enter the length in Hours, Minutes and Seconds. The page opens with 5 minutes already set.
3. Type a Label (optional), for example Tea or Presentation. It appears above the digits and again in the message when time is up.
4. Keep Play a sound when time is up ticked for an alarm, or untick it for a silent timer.
5. Press Start. The button changes to Pause and then Resume. Reset restores the full time, and Full screen enlarges the clock so it can be read across a room.

Space starts and pauses, and R resets while the timer is stopped, as long as the cursor is not in a text box.

The digits read MM:SS, and switch to HH:MM:SS once an hour or more is set. A bar fills as time passes, and the tab title shows the time left, for example 04:12 left, so you can watch it from another tab. When the count reaches zero the digits flash, the note says Time is up together with your label, and, if sound is on, a short alarm plays: three quick beeps and a higher, longer one. The browser generates these tones itself, so no audio file is downloaded. While the timer runs it also asks the browser to keep the screen awake, where the browser supports that.

The fields are added together, so 90 in the Minutes box is the same as 1 hour 30 minutes. Some real settings:

The last row shows 01:15:00 on the display. If a recipe or exam gives its time as decimal hours, the time converter turns 1.75 hours into 1 hour 45 minutes. The timer measures against the system clock instead of counting ticks, so a tab that the browser slows down while hidden still shows the correct time left when you return.

The countdown timer only runs while its page is open. Closing the tab stops it, and on a phone a locked screen can pause the page and silence the alarm. There are no push notifications, so it cannot wake you from another app. For anything where a missed alarm matters, such as medication or a safety-critical step, set a second alarm on your phone or use a kitchen timer as a backup.

• Durations only. It counts a length of time, not a time of day, so it cannot ring at 7:30. To work out the gap between two dates, use the date difference calculator.
• Maximum. The Hours box goes up to 99 and the Minutes box up to 999.
• Changing a time mid-run. Edits to the fields while it is running update the display only. Press Reset to apply a new time. If the time is zero, the page asks you to set one.
• Sound. A muted tab, low volume or strict autoplay rules can silence the alarm. Pressing Start counts as the interaction that lets the browser play it.
• Late alarms. Browsers slow hidden pages, so the alarm can arrive a moment late in a background tab even though the displayed time is right. Keep the tab visible if timing matters.

To measure how long something takes rather than limit it, use the online stopwatch. To repeat work and break periods automatically, the Pomodoro timer chains them for you.