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Temporizador de contagem regressiva

Contagem regressiva precisa em horas, minutos e segundos com alerta sonoro.

Countdown

Presets:

Como funciona

  1. Remaining time is derived from a monotonic clock and recomputed on every display update (never by counting ticks), so background-tab throttling can never make the countdown drift.
  2. The interval loop only refreshes the display; the source of truth is “end instant − now”, so returning to a throttled tab shows the correct remaining time immediately.
  3. Completion is detected the same way: when remaining time reaches zero, the timer flips to “finished”, announces it, and (optionally) plays a short chime.

Informações úteis

  • The chime is optional and off by default; your browser allows audio here because starting the timer is a user action. It will not wake a locked or sleeping device.
  • Closing or reloading the page ends the timer: a web page cannot run timers for a tab that no longer exists.
  • Keyboard: Space starts/pauses, R resets (ignored while you are typing in a field).
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Perguntas frequentes

Will the timer stay accurate in a background tab?
Yes. Browsers throttle background timers, but this timer measures real elapsed time with a monotonic clock and recomputes the display, so returning to the tab shows the correct remaining time.
Does it sound an alarm?
Optionally: a short chime plays on completion if enabled, using browser audio. It will not sound if your device is fully locked or sleeping.
What happens if I close or reload the page?
The timer stops: a browser page cannot run timers for a closed tab. For countdowns that must survive closing, use a system timer or keep the tab open.