Stopwatch

Reference

How does this online stopwatch work?

This stopwatch uses the performance.now() Web API for sub-millisecond precision timing. Unlike Date.now(), which can be affected by system clock adjustments (NTP sync, daylight saving changes), performance.now() uses a monotonic clock that only moves forward — ensuring accurate, drift-free measurements for the duration of your timing session.

Lap time vs split time — what is the difference?

Total time: The cumulative time elapsed since the stopwatch started, shown for each lap. This tells you the absolute point in time when you pressed Lap.
Split time: The duration between consecutive lap presses — the time for just that individual segment. Useful for comparing performance across intervals: if your 5th split is slower than your 3rd, you can see exactly by how much. Both values are recorded automatically when you press the Lap button.

Stopwatch use cases

Sports & training — record lap times for running intervals, cycling splits, swimming sets, or any timed exercise. Presentations — time individual segments of a talk to stay within your allotted time. Process timing — measure how long each step in a workflow, build process, or cooking recipe takes. Productivity — time focused work sessions (Pomodoro technique: 25-minute work intervals). Education — time exams, quizzes, or student presentations. Export lap data as CSV or JSON for further analysis in a spreadsheet.

Privacy

The stopwatch runs entirely in your browser. No timing data is sent to any server.