00:00:00.000
Ready
Space Start/Pause • L Lap • R Reset • E Export
Settings
50%
Precision timing with lap functionality and millisecond accuracy
This professional stopwatch provides millisecond-precision timing for sports, productivity tracking, and any activity requiring accurate time measurement.
The stopwatch uses JavaScript's performance.now() API for high-precision timing. Rather than incrementing a counter, it stores the start time and calculates elapsed time on each update, ensuring accuracy even if the browser tab is backgrounded or the system experiences lag.
Lap Time: Time for the current lap only (difference between consecutive lap recordings)
Split Time: Total elapsed time from start to the lap recording
This stopwatch uses the browser's high-resolution timer (performance.now()) which provides sub-millisecond precision. Actual resolution varies by browser and context: typically 100 microseconds (0.1 milliseconds) in standard use, 1 millisecond in Firefox with default privacy settings, or up to 5 microseconds in specially configured cross-origin isolated contexts. The display shows milliseconds (1/1000th of a second), which is more than sufficient for sports timing, productivity tracking, and most professional applications. The timer continues running accurately even when the browser tab is in the background, as it calculates elapsed time from the stored start timestamp rather than relying on interval callbacks.
Yes! After recording lap times, use the "Export CSV" button to download your data in a spreadsheet-compatible format. The CSV includes lap number, lap time, and split time for each recording. You can also use "Copy to Clipboard" to paste the data directly into any application. This is particularly useful for athletes analyzing training sessions, coaches tracking team performance, or anyone doing time-motion studies.
Lap time is the duration of just that individual lap (the time between consecutive lap recordings). Split time is the total elapsed time from when you started the stopwatch to that lap point. For example, if you record laps at 1:00 and 2:30, the second lap's lap time is 1:30 (the interval), while its split time is 2:30 (total elapsed). Use lap times to compare individual segment performance, and split times to track overall progress.
No, closing the tab will stop the timer. However, the timer does continue running accurately if you switch to a different tab or minimize the browser window. Modern browsers may throttle background tabs to save battery, but our stopwatch compensates for this by calculating elapsed time from the start timestamp rather than relying on regular interval updates. For long timing sessions where you need to close the browser, consider keeping the tab open or using a dedicated desktop timer application.
The stopwatch displays up to 99 hours, 59 minutes, 59 seconds, and 999 milliseconds (99:59:59.999). This covers virtually any timing need, from sprint intervals to ultramarathons to multi-day productivity tracking. If you reach the maximum, the timer will continue running but the display will overflow. For most practical applications, the stopwatch handles durations far beyond typical use cases.
Press Space to start/pause the timer, L to record a lap, R to reset, and E to export lap data. Keyboard shortcuts are significantly faster than clicking buttons, especially for precise timing. When your finger is positioned over the spacebar, you can react more quickly than moving a mouse cursor to a button and clicking, which can provide a faster response. For example, when timing sprints, position your finger over the Space bar and press it the instant the event begins or ends. The shortcuts work even when the timer display isn't focused, making them ideal for quick reactions.
The stopwatch automatically identifies your fastest lap (highlighted in green) and slowest lap (highlighted in red) to help you analyze performance. This visual indicator makes it easy to spot your best effort and identify laps where you may have slowed down. For training purposes, aim to keep your laps close to your best time for consistent performance, or use the green lap as a target to beat in future sessions.
This stopwatch interface shows one timer at a time. However, you can open multiple browser tabs or windows with the stopwatch to run several timers simultaneously. Each tab operates independently, allowing you to time different activities, athletes, or work tasks in parallel. For complex timing needs with many simultaneous timers, consider using a dedicated multi-timer application designed for that purpose.
The stopwatch is optimized for efficiency, updating the display 100 times per second (every 10 milliseconds) which provides smooth visual feedback while minimizing CPU usage and battery drain. For very long timing sessions (over an hour), consider keeping your device plugged in. Closing other browser tabs and applications can also help extend battery life. The timer's efficient design means it uses less battery than video streaming or resource-intensive web applications, making it suitable for mobile timing when needed.
Your settings (sound, notifications, volume) are automatically saved to your browser's local storage and will persist across sessions. However, the active timer and lap times are not saved if you refresh or close the page - this is intentional to prevent accidentally losing timing data during active sessions. Always export your lap times using the "Export CSV" or "Copy to Clipboard" buttons before closing the page if you need to save them for later analysis.