Skip to the tools
All kits

Classroom timer

Set a countdown for an activity, or run the stopwatch, on a display big enough to read from the back of the room. A gentle chime sounds when a countdown reaches zero.

The time is worked out from the clock, so it stays right even if the tab was in the background, and nothing is stored.

5:00

The timer runs in your browser and chimes softly when a countdown ends. Keep the tab visible on the board.

Questions

Is my class data sent anywhere?
No. Every tool here runs in the page itself. There is no server that receives your students' names or their marks, and you can check it in your browser's network tab: using a tool produces no request carrying what you typed. The one thing this site stores is an email address, given at the point you download or copy a result.
Will it keep time in a background tab?
Yes. Browsers slow timers in hidden tabs, so this works the remaining time out from the clock rather than counting down by one each second, and it is right whatever the browser did while it was hidden.
Where does the chime come from?
It is generated in the page, two soft tones with a gentle envelope. No sound file is downloaded. Browsers only allow audio after you have interacted with the page, so the chime works because you pressed start.
Can students see it from the back?
That is the point of the large display. Put the tab full screen on the board and the digits fill the space, so a countdown is readable across the room.

The other tools here