Countdown
Countdown
Full screen turns this into a room display: very large digits, high contrast, and no advertising on screen.
This browser does not offer the Screen Wake Lock API, so the display can still dim or sleep while the timer runs. Set the screen timeout on the device before a talk or a class.
Count a duration or a fixed date and time, full screen, with your own message under the clock.
Two ways to count
Duration mode counts a length of time — five minutes for a presentation slot, ninety seconds for a demo, forty minutes for an exam section. Date-and-time mode counts to a fixed instant: doors at 19:30, a launch on Friday, midnight on New Year's Eve. Both read the same clock, so you can switch between them without losing your place.
Built for a room, not just a desk
Full screen turns the page into a room display: oversized digits, high contrast, no navigation, and no advertising on screen. Your message sits under the clock, which is usually all an audience needs — Doors close, Break ends, Round two. Press Escape or use the exit button to come back.
It does not drift, and it survives a reload
The countdown stores the instant it should reach zero and recomputes the remaining time from the system clock several times a second. Nothing is accumulated tick by tick, so an hour-long countdown ends when it should rather than seconds late. Reloading the page mid-count restores the same target, because that target is what was saved — not a number of seconds left.
Daylight saving is handled honestly
A date-and-time countdown is measured against the wall clock in this device's own time zone. If the clocks change between now and the target, the countdown is an hour shorter or longer than the calendar suggests, which is exactly what will happen in the room.
Questions
- Can I share a configured countdown?
- Yes. Copy preset link produces a URL that carries the setup, such as ?d=25m for a twenty-five minute countdown or ?at=2026-12-25T09:00 for a fixed instant, with an optional &msg= for the message under the clock. Anyone opening that link gets the same timer.
- What happens if I reload while it is running?
- The countdown resumes at the correct remaining time. The target instant is stored in this browser and the remaining time is recalculated from it on load, so a reload costs nothing.
- Will my screen stay awake in full screen?
- Where the browser supports the Screen Wake Lock API, yes — the timer holds a lock while it is running and this tab is visible. Where it does not, the page says so rather than pretending, and you should raise the device's own screen timeout.
- Does the tab title show the countdown?
- Yes. While the countdown runs, the browser tab shows the remaining time, so a backgrounded timer is still readable from the tab strip.