Full-Screen Countdown Timer

Why most online timers drift

Open a countdown in one tab, switch to another for a few minutes, and come back: it's often behind. That isn't a bug in one site so much as how browsers work. To save battery, they slow down or freeze timers in tabs you aren't looking at. A timer that counts by subtracting one second on its own schedule simply misses some of those seconds, and the error adds up.

This timer doesn't count its own seconds. When you press Start, it records the exact clock time it should reach zero, and every update just asks the system clock how long is left. Throttling a background tab changes how often the number on screen refreshes, but not what it says — the instant you look back, it's right. For a classroom or an exam, that's the difference that matters.

Built for the front of the room

• Big enough for the back row. Full screen fills the display with the clock and nothing else.
• Projector without the clutter. Send it to a second screen and the room sees a clean clock on white while your controls stay on your laptop.
• A clear finish. The clock turns red at zero, says time's up, and chimes — with the chime easy to switch off.
• Label it. "Break", "Quiz", "Warm-up" — a caption above the clock so the room knows what it's for.

Good for more than lessons

• Exams and tests — where drifting even a minute is a real problem.
• Workshops and talks — keep segments and breaks on schedule on the main screen.
• Timeboxed work — pomodoro sessions, standups, and anything you want visible across the room.

Questions