Eleven hours is an awkward long watch, useful when a process finishes late in the day and you need the reminder more than the view. Pair it with a written note of what to do at the end. The alarm does not contain the instructions.
Test the sound once at the start. Eleven hours is a bad time to discover the tab was muted. 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 11 hours 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 11 hours timer on a projector?
Press start, then F or the fullscreen button. Classroom mode hides the writing so the digits fill the wall. Test the sound once at the start. Eleven hours is a bad time to discover the tab was muted.
What is 11 hours actually good for?
Eleven hours is an awkward long watch, useful when a process finishes late in the day and you need the reminder more than the view.
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.