Twenty-six minutes gives a Pomodoro a one minute cushion for writing down where you stopped. It is a fair length for a student explanation: model, then they try, then you listen.
Keep the last minute for the note. Future you cannot reconstruct a stopping point from a blank page. 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 26 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 26 minutes timer on a projector?
Press start, then F or the fullscreen button. Classroom mode hides the writing so the digits fill the wall. Keep the last minute for the note. Future you cannot reconstruct a stopping point from a blank page.
What is 26 minutes actually good for?
Twenty-six minutes gives a Pomodoro a one minute cushion for writing down where you stopped.
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.