What is a 15 minute timer?
A 15 minute timer is an online countdown that runs for exactly 15 minutes and alerts you when it reaches zero. This one is already set when the page opens: press Start or the space bar and it counts down from 15:00, keeps exact time if you switch tabs or lock your phone, and rings until you stop it.
What 15 minutes is good for
Fifteen minutes is a quarter hour: a stand-up meeting, a quick walk, the first "just start" block when a task feels too big, a short nap that still avoids deep sleep, and the long break of a Pomodoro cycle after four focus sessions. In the kitchen it is simmering white rice after it comes to the boil, with another 10 minutes of resting off the heat.
Many teachers use 15-minute activity timers because the shrinking ring is easier for a class to read than a clock. Press F for the full-screen view: large digits, no menus, Esc to leave.
Start it in one click
There is nothing to set: the time is loaded, the Start button has keyboard focus on a computer, and the alarm sound, volume and screen settings are remembered from your last visit. If you need a different length, type it into the hours, minutes and seconds boxes or pick another preset below the timer.
It keeps counting in a background tab
The end time is fixed the moment you press Start, so a slow or sleeping tab cannot make it late: whenever the page is drawn it recomputes the remaining time from the clock. The alarm is pre-scheduled on the browser's audio clock and backed by a system timer and a desktop notification, and if the device was asleep when the time came, the page rings as soon as you return and shows how long ago the 15 minutes ended. On iPhone keep the tab on screen, since Safari pauses hidden pages; Keep screen on, which is on by default on phones, prevents auto-lock while it runs.
Alarm, repeat and phone use
Choose Beep, Bell, Digital, Soft, Cuckoo, Chime, Pipe or None and set the volume; all but the cuckoo are generated in the browser and work offline, and the cuckoo is a short clip of about 65 KB fetched once and then kept by the browser. The alarm repeats until you press Stop alarm, Space or Esc, and gives up after 60 seconds. Android phones vibrate as well; iPhones on iOS 17 or later play it even with the silent switch on.
Need a slightly different time?
Neighbouring presets are the 10 minute timer and the 20 minute timer. A 17-minute task: start this one and press +1 min twice. For a longer timed cycle of work and rest, the Pomodoro timer uses 25 and 5 minutes by default.
Other time tools
For measuring how long something takes, use the stopwatch, which counts up and records laps. For the days and hours until a date, use the countdown. For alternating focus and break periods, the Pomodoro timer runs the whole cycle, and the interval timer repeats work and rest rounds for training. They all share this timer's clock engine, sounds and settings.