Stopwatch & Countdown Timer

A stopwatch counts upward from zero and is used to measure how long something takes. A countdown timer starts from a set time and counts down to zero, then triggers an alert. Use a stopwatch when you want to measure elapsed time (e.g. how long a build takes). Use a countdown timer when you want to be notified after a fixed period (e.g. 25-minute Pomodoro session).

The Pomodoro Technique is a time management method developed by Francesco Cirillo. The process: set a timer for 25 minutes (one "Pomodoro"), work on a single task without interruption, take a 5-minute break, then repeat. After 4 Pomodoros, take a longer 15–30 minute break. The technique helps maintain focus, reduce fatigue, and improve output quality.

A lap captures the elapsed time at a specific point without stopping the main timer. For example, if you are timing a race, you can press Lap at the end of each circuit to record the time for that specific lap. The main timer continues running. This gives you both the split time (time for that lap alone) and the cumulative elapsed time.

Browser stopwatches use JavaScript's performance.now() or Date.now() APIs, which have millisecond-level precision. However, the browser's rendering loop (typically 60fps = 16.7ms intervals) means displayed updates occur at 60fps. The underlying timing is accurate to ~1ms. This is sufficient for all everyday tasks — professional athletic timing requiring sub-millisecond accuracy uses dedicated hardware.

Modern browsers throttle JavaScript execution for background tabs to save battery and CPU. A stopwatch that only updates the UI may appear paused when the tab is hidden. However, the actual timer uses a timestamp-based approach — it records when the timer started, so when you return to the tab, the elapsed time is calculated correctly from the start timestamp, not from UI update intervals.

Time-boxing is a productivity technique where you allocate a fixed time period (a "box") to a task, then stop when time is up regardless of completion. This prevents perfectionism and scope creep, creates urgency (Parkinson's Law: work expands to fill available time), and helps prioritise what matters most. Combined with a stopwatch or countdown timer, time-boxing is a core technique in Agile, Scrum, and personal productivity systems.