Fifteen minutes is a quarter of an hour, a short meeting, and a reading block you can schedule without apologizing. It is long enough for a real task: a form, a set of problems, a warm-up that includes the hard part.
If a conversation needs a boundary, put fifteen minutes on the projector. People behave better when the end is visible. Press space to start or pause, R to reset, and F for fullscreen. The screen can stay awake after you start, using the wake lock your browser allows. Pick the alarm before you begin. A bell, a chime, a beep, or a short digital pulse all come from the Web Audio API, so there is no sound file to wait on.
This page is the 15 minutes countdown and nothing else is running underneath it. Related lengths are linked under the guide if you want a neighbor, and the timer itself stays above the fold.
Questions
How do I run a 15 minutes timer on a projector?
Press start, then F or the fullscreen button. Classroom mode hides the writing so the digits fill the wall. If a conversation needs a boundary, put fifteen minutes on the projector. People behave better when the end is visible.
What is 15 minutes actually good for?
Fifteen minutes is a quarter of an hour, a short meeting, and a reading block you can schedule without apologizing.
Will the countdown drift if I switch tabs?
No. The end is a timestamp. The display is the gap between that timestamp and now, so a background tab does not lose seconds the way a ticking counter would.