Stopwatch
An online stopwatch with lap times, accurate to hundredths of a second and unaffected by browser throttling.
How it works
The elapsed time is the difference between now and the moment you started, not a counter incremented on a tick. That distinction matters: a counter drifts if the browser throttles the page in a background tab, whereas a difference against the clock stays correct however irregularly it is redrawn.
The display refreshes about twenty times a second, which is enough to look smooth. The underlying figure is exact regardless of how often it is painted.
Laps record the total at the moment you press, and the split is the gap since the previous lap. Both are shown, because runners want splits and process timing usually wants cumulative totals.
The formula
Elapsed
elapsed = now − start time + previously accumulated
Split
split = this lap total − previous lap total
Display
hh:mm:ss.cc
Worked examples
| Scenario | Working | Result |
|---|---|---|
| Start, wait, stop | Difference against the clock | Exact elapsed time |
| Pause and resume | Accumulated plus new span | Paused time is excluded |
| Three laps | Totals and splits | Both columns recorded |
When you'd use it
- Timing intervals in training
- Recording lap or split times
- Timing a process or a task
- Anything needing a stopwatch without installing one
Common questions
Does it keep running if I switch tabs?
Yes, and it stays accurate. Browsers throttle background timers, so a stopwatch that counted ticks would fall behind — this one measures the difference against the clock, so the elapsed figure is correct when you come back regardless of how often it was redrawn.
What is the difference between a lap and a split?
The lap column shows the total elapsed at the moment you pressed; the split shows the time since the previous lap. Runners usually want splits, process timing usually wants totals, so both are recorded.
Are my times saved?
Only while the page is open. Nothing is uploaded and nothing persists — reloading clears the stopwatch and its laps.