Countdown Timer

Your local timezone. The datetime-local input doesn’t carry timezone info, so when you type 2026-12-31T23:59, that’s interpreted as 11:59 PM in your local time. The Share URL converts to UTC ISO format so it travels correctly across timezones – when the recipient opens the link, their browser converts back to their local time, preserving the same absolute moment.

Modern browsers throttle setInterval in background tabs (to ~1 Hz minimum, but the actual fire rate can be slower). The display might briefly show a “stale” value, but it self-corrects on next tick because compute() uses Date.now() directly – not an accumulated counter. So the displayed time stays accurate even after the tab regains focus.

Browsers block AudioContext from playing until the user has interacted with the page (a security feature against autoplay). If you start the timer immediately on load, the first beep may be silent. Click somewhere first, or just trust the visual + tab-title alert.

Yes – when the timer expires, the document title becomes ⏰ Expired - Free Countdown Timer.... This is visible in the tab strip even when you’re on a different tab.

After the timer hits zero, instead of stopping, it counts upward to show how much time has passed since the deadline. Useful for tracking overruns (“how late am I?”).

Sub-second accurate. The display ticks every 1000ms but the calculation uses Date.now(), so even if a tick is delayed (background tab, system lag), the next visible update shows the correct value. For sub-second precision, this isn’t the right tool – use a stopwatch.

The timer stops. Re-open with a Share URL to resume from the same target – the displayed countdown will reflect “time remaining from now,” not “time remaining from when you set it.” For a persistent timer that runs even when the tab is closed, you’d need a service worker (out of scope).

Pause freezes the display but doesn’t change the target – when you resume, the count jumps to “actual current remaining time,” not “remaining time when you paused.” If you want pause to add to the target instead, you’d need a stopwatch (which adds elapsed time) or a different timer model.

No. Everything runs locally in your browser – nothing is sent to a server, logged, or stored, and the tool keeps working offline once the page has loaded.

Either the input is empty or the date you typed is unparseable. Use the date picker or the preset buttons to be sure.