Countdown Timer
A fullscreen countdown timer for lessons, tests, group work and transitions. Set it from a preset or type an exact time, start it, and the whole class can see how long is left. When more time is needed you can add it while the clock is still running, without losing your place.
Quick Presets
Save Current Time
How to use the countdown timer
Set the time
Tap a Quick Preset — 1, 5, 10, 15, 30 or 45 minutes, or an hour — or type the exact hours, minutes and seconds you need.
Start the countdown
Press Start, or tap Space. A progress bar runs alongside the digits and changes colour as the time runs down, so the room can read the state from across the room.
Add time if you need it
Press +1, +5 or +10 minutes at any point — including while the timer is running. The deadline extends and the clock carries on, so 'two more minutes' does not mean starting again.
Show it on the board
Press F or the fullscreen button so the digits fill the screen.
Save a setup you reuse
Give a duration you use often a name and save it as a preset. It is stored in your browser and waiting for you next lesson.
Frequently asked questions
- Can I add time without restarting?
- Yes. The +1, +5 and +10 minute buttons work while the timer is running. They push the finish time back and the countdown continues from where it was.
- Will it make a sound when time is up?
- Yes, if sound is switched on. There is an alarm at zero and a warning shortly before, and the screen can flash as well. Sound is off by default so the timer never surprises a quiet room.
- Can I save the times I use every week?
- Yes. Enter the duration, give it a name and save it as a preset. Saved presets stay in your browser between lessons.
- Are my settings remembered?
- Yes. Sound, the progress bar, the flash at the end, the warning time and the colour theme are all stored on your device and restored the next time you open the timer.
ClassBox is free and has no ads, no accounts and no trackers. The countdown timer runs entirely in your browser — whatever you type stays on your device.