Stopwatch
Laps, splits and keyboard control
A stopwatch measures elapsed time between a start and a stop, with laps recording intermediate points along the way. The distinction worth knowing is between a lap and a split: a lap is the time for one segment on its own, while a split is the total elapsed at that point. Most tools show both, and confusing them makes a set of times meaningless.
Accuracy in a browser comes from measuring against a monotonic clock rather than counting timer callbacks. A timer that fires every ten milliseconds will drift, because callbacks are throttled in background tabs and delayed under load. Reading the elapsed time from a clock at each render keeps the display correct regardless of what the browser did in between.
How to use it
- Start and stopBegin timing, and stop when you are done. Keyboard control means you are not hunting for a button while trying to watch something else.
- Record laps as you goEach lap captures the segment time and the running total, so a set of intervals can be compared without arithmetic afterwards.
- Copy the resultsTimes can be copied out into a note or a spreadsheet. Nothing is recorded anywhere else — closing the tab discards them.
Frequently asked questions
What is the difference between a lap and a split?
A lap is the duration of one segment measured from the previous lap marker. A split is the cumulative time from the start to that marker. Four laps of thirty seconds give splits of 30, 60, 90 and 120 seconds. Runners usually think in splits; anyone timing repeated identical tasks usually wants laps.
Does the timer keep running if I switch tabs?
Yes. Because elapsed time is computed from a clock rather than accumulated from timer ticks, the value stays correct even though browsers throttle background tabs heavily. The display may not repaint while hidden, but it will be right the moment you return.
How accurate is a browser stopwatch?
Accurate enough for anything human-timed. Timer resolution is deliberately reduced in browsers as a defence against timing attacks, so sub-millisecond precision is not available — but your reaction time in pressing start is measured in tenths of a second, which dwarfs any clock error.
Will I lose my times if I reload?
Yes. Everything is held in memory for the life of the page, which is what keeps the tool free of storage and tracking. Copy anything you need before closing or refreshing.
Can I use this while offline?
Once the page has loaded, yes — no network request is made while it runs. That follows from how it works rather than being a feature: there is no server involved in timing anything.