Millisecond stopwatch
Time anything to the hundredth of a second. Start, stop, and split with the buttons or the keyboard, and keep every lap in view.
Space start/stop · L lap · R reset
How to use the millisecond stopwatch
Start and stop
Begin timing with the button or the keyboard. Elapsed time is measured against a high-resolution clock, so it does not drift the way a counter incremented per frame would.
Record laps
Take a split without stopping the clock. Each lap shows both its own duration and the cumulative total.
Compare the splits
The lap list is where the information is — consistency, or a clear fade, shows up across splits in a way a single total cannot.
Reset when you are done
Clear the clock and the laps for a fresh measurement.
Timing accurately in a browser
A stopwatch is only useful if it is honest about its precision. This one measures against the browser's monotonic high-resolution clock rather than by counting animation frames, so pausing, tab-switching or a busy CPU does not silently lose time. What is displayed to the millisecond is measured to the millisecond.
The limit is not the clock but the loop between you and it. Human reaction time is roughly 200 to 250 milliseconds, so any hand-triggered measurement carries that much uncertainty at each end. Displayed milliseconds are real for comparing splits taken the same way; they are not a claim that you timed a sprint to the thousandth.
Laps are what turn a stopwatch into an instrument. A total tells you the outcome; splits tell you the shape of it. A set of laps that widen steadily and a set that hold flat can produce the same total and describe completely different performances.
Everything runs locally and nothing is recorded anywhere. Closing the tab discards the session, so copy anything you want to keep before you leave.
When it comes in handy
Training intervals.
Time repeats and compare the splits across a set.Cooking and brewing.
Coffee, tea and anything else where thirty seconds changes the result.Presentation practice.
Time a talk section by section to find what needs cutting.Benchmarking by hand.
A rough measure of how long a manual process takes, repeated.Classroom experiments.
Lap timing for a physics or sports-science exercise.Focus tracking.
Measure how long you actually stay on a task before switching.
Questions & answers
- How precise is it?
- It's driven by the browser's high-resolution clock and displays hundredths of a second. Because it uses elapsed real time rather than counting frames, it stays accurate even if the tab is briefly backgrounded.
- What are the keyboard shortcuts?
- Space starts and stops, L records a lap while running, and R resets. It works without touching the mouse.
- What does a lap show?
- Each lap lists the split (time since the previous lap) and the total elapsed time at that point.
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