Forty-five seconds is a long rest or a short drill: one passage, one explanation, one hold. People underestimate it. They start a story and the alarm catches them, which is useful.
Pick the beep if the room is loud. Pick the chime if you are the only one listening. The countdown is a timestamp, not a chain of ticks. If you switch tabs, the digits catch up when you return, and a scheduled end still fires the alarm as soon as the browser allows it. Space starts and pauses. R resets. F fills the screen.
This page is the 45 seconds 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 45 seconds timer on a projector?
Press start, then F or the fullscreen button. Classroom mode hides the writing so the digits fill the wall. Pick the beep if the room is loud. Pick the chime if you are the only one listening.
What is 45 seconds actually good for?
Forty-five seconds is a long rest or a short drill: one passage, one explanation, one hold.
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.