Stopwatch & Lap Timer

A lap timer records intermediate times — called splits or laps — during a continuous timing session. Unlike a basic stopwatch that only shows elapsed time, a lap timer captures the exact duration of each segment while the clock keeps running. Modern browser-based lap timers leverage the Performance API for sub-millisecond resolution, making them accurate enough for serious training use.

Tracking lap splits reveals performance trends that total time alone cannot show. A runner finishing a 5K in 25 minutes might discover their first kilometer was 4:30 but their last was 5:45 — a clear pacing problem. Coaches use split data to design interval workouts, monitor fatigue onset, and adjust training intensity. Outside sports, lap timing helps with time audits and task measurement.

Browser timers use the high-resolution Performance API providing timestamps accurate to 5 microseconds. Lap times are computed as the difference between consecutive timestamps, ensuring accuracy is not affected by display update intervals. Background tabs may throttle timers, but timestamp-based calculation remains accurate.

Keep the browser tab in the foreground during timing. Tap the Lap button precisely at each transition point. Review your splits immediately after a session and copy them before closing the page. For sports training, combine lap data with heart rate monitoring to correlate pace with effort.