Stopwatch
A big, precise stopwatch with lap times โ space bar to start.
Using the stopwatch
Space starts and stops; L records a lap. Laps show both the split (that lap alone, with the fastest in green and slowest in red) and the running total โ the format coaches and runners actually want. The display reads to hundredths of a second.
Why it doesn't drift
Cheap stopwatch pages accumulate time tick by tick, so a busy device or a backgrounded tab quietly loses seconds. This one records the moment you press start on the browser's monotonic clock and always displays true elapsed time โ switch tabs for ten minutes and it is still exactly right.
Worth knowing when timing by hand: your reaction time adds roughly a quarter second at each end (the reaction test will show you yours), which is why hand-timed sprints are systematically flattering. For counting down instead of up, the timer and countdown are the right tools, and the chess clock handles two players taking turns.
Frequently asked questions
How do I start the stopwatch with the keyboard?
Space starts and stops, L records a lap. No clicking required, which also keeps your reaction time out of the buttons.
What is the difference between split and total?
The split is that lap alone; the total is time since the start. Both are shown per lap, with the fastest and slowest splits colour-coded.
Does it keep running if I switch tabs?
Yes โ elapsed time is measured against the clock from the start press, not accumulated in ticks, so backgrounding the tab cannot make it drift.
How accurate is it?
The display reads to 0.01 s and the measurement is as good as the device clock. The limiting factor is human: pressing at each end adds around a quarter of a second.