Stopwatch
A timestamp-accurate online stopwatch with start, stop, lap, and reset, plus a lap table with splits and totals.
Processed locally in your browser — nothing is uploaded.
Stopwatch
About Stopwatch
Start, stop, lap, and reset with a display precise to hundredths of a second. Time is measured from system timestamps rather than by counting screen updates, so the reading stays accurate even when the tab is throttled in the background.
Each lap records both its split (time since the previous lap) and the running total.
Common uses
- Time workouts, intervals, and rest periods
- Track how long tasks actually take
- Record lap splits for practice runs
Example
Input
Lap pressed at 01:00.00 and 02:30.00
Output
Lap 2 — split 01:30.00, total 02:30.00
Frequently asked questions
How accurate is an online stopwatch?
Accurate to well under a tenth of a second for practical timing, because elapsed time is computed from system-clock timestamps rather than by counting screen refreshes. The display updates about 30 times a second and shows hundredths.
Does the stopwatch keep running if I switch tabs?
Yes. Since time is measured as the difference between real timestamps, backgrounding the tab only slows the display updates, not the measurement — when you come back, the reading is correct.
Are my recorded times saved or uploaded anywhere?
No. The stopwatch runs entirely in the page and keeps laps only in memory — nothing is transmitted, and reloading the tab clears everything, so copy any splits you want to keep.
What's the difference between a lap split and the lap total?
The split is the time since the previous lap press — one interval on its own — while the total is the running time from the very start. Splits tell you how each segment compared; totals tell you where you were overall.