Curio

Stopwatch & Timer

Accurate stopwatch with split laps and countdown timer that never drifts in asleep tabs.

Productivity
00:00.00

Accurate timekeeping in web browsers is deceptively tricky. Many online stopwatches and kitchen timers rely on naive interval counters that add a fraction of a second on every clock tick. The moment a user switches tabs, minimizes a window, or allows their laptop screen to lock, the operating system and browser throttle timer executions to conserve battery. When you return ten minutes later, a naive timer might have only counted two minutes forward.

This stopwatch and countdown timer avoids interval drift entirely. The stopwatch anchors itself to high-resolution monotonic timestamps (performance.now()), which remain strictly linear and immune to system clock adjustments. The countdown timer anchors itself to an absolute wall-clock target deadline. Even if your machine enters deep sleep for three hours, the timer evaluates the true delta the instant the tab wakes up, immediately showing whether the deadline passed and exactly how much overrun has elapsed.

Split laps and timing analysis

The stopwatch supports unlimited lap tracking with split calculations. When recording multiple splits—such as track intervals, swim repetitions, or multi-step kitchen recipes—the tool records both the isolated lap duration and the cumulative time. Once three or more laps are logged, the interface automatically pinpoints and highlights your fastest and slowest laps, making pace variations effortless to spot at a glance. You can copy the complete lap breakdown to your clipboard formatted as clean text for workout logs or spreadsheet reports.

Countdown presets and overrun tracking

For standard tasks like boiling eggs, steeping tea, presentations, or study sprints, dedicated preset buttons provide instant one-click setup. When the countdown reaches zero, a synthesized multi-tone chime rings and the tab title updates so you notice the completion even while working in another program. Rather than stopping dead at zero, the display seamlessly counts up into an overrun readout, informing you exactly how many minutes or seconds ago your timer expired.

If you prefer a structured work-rest cycle with automated short and long breaks, pair this with our dedicated Focus Timer.

Controls

SpaceStarts or stops the stopwatch or countdown timer.
LRecords a lap split while the stopwatch is running.
RResets the active stopwatch or timer to its initial state.
EscapeSilences the alarm tone when the countdown reaches zero.

Questions

Does the timer keep running accurately when the tab is hidden or backgrounded?

Yes. Standard web timers often drift because web browsers aggressively throttle background tab intervals down to once per second or suspend them during device sleep. This tool calculates elapsed time directly from hardware timestamps on every tick rather than counting tick intervals, guaranteeing zero drift when you switch back.

Will a running countdown survive if I accidentally refresh or close the page?

Yes. The countdown timer persists its target completion timestamp in your browser's local storage. If you refresh the page or restart your browser, the timer restores immediately and will correctly indicate if the timer finished while the window was closed.

Why did no audio chime play when the timer reached zero?

Modern browsers restrict automated audio playback until the visitor interacts with the page at least once. Pressing Start, adjusting presets, or clicking anywhere in the tool satisfies this browser policy and allows the alarm chime to sound.

How does the full-screen display work?

Clicking the Full Screen button expands the numerical readout across your entire monitor, hiding non-essential controls and styling the digits for high visibility from across a room, gym floor, or kitchen. Pressing Escape or clicking Exit returns to the standard view.