Online stopwatch with lap times
Start, pause, lap and reset, with a laps table that marks the fastest and slowest lap. Timed with the browser's monotonic clock.
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Press Start and the display counts up in hundredths of a second. Lap records the time since the previous lap and the running total; the table highlights the fastest and slowest lap once you have two or more, and "Copy laps" gives you tab-separated text you can paste into a spreadsheet.
Timing uses performance.now(), a monotonic clock defined by the W3C High Resolution Time specification. Unlike the wall clock it never jumps when the computer syncs its time or changes for daylight saving, so a long run stays correct. Browsers round its value slightly for security, far below the hundredth of a second shown here.
With the stopwatch panel focused, Space starts and stops, L records a lap and R resets, so you can time without looking at the mouse. In practice your reaction time when pressing a key (typically around 0.2 seconds) is a bigger source of error than the clock itself.
How to use it
- Press Start (or focus the stopwatch and press Space).
- Press Lap (or L) at each split; the laps table fills in with lap time and total.
- Press Pause (or Space) to stop; Resume continues from the same time.
- Copy the laps if you need them, then Reset (or R) to start over.
Frequently asked questions
Does it keep running in a background tab?
Yes. Elapsed time is computed from the start moment, so it is right when you return even if the display stopped updating while the tab was hidden.
How precise is it?
The clock is precise to well under a millisecond, and the display shows hundredths. The real limit is human: pressing a button or key takes a variable fraction of a second.
What is the difference between lap time and total?
Lap time is the time since the previous lap (or since the start for lap 1). Total is the elapsed time on the stopwatch when you pressed Lap.
Are my laps saved?
No. Laps live only in this page; copy them before you reset or close the tab.
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