Chronometer

A precise, no-nonsense online stopwatch. Start it, pause and resume as often as you like, record splits (laps), and reset — all timed to the hundredth of a second and controlled entirely from the keyboard if you prefer. It runs in your browser; nothing is uploaded and nothing is stored.

How do I use it?

Press Start (or the space bar) and the clock begins. Press it again to pause, and once more to resume from where you left off. Hit Split (or the L key) at any point to stamp the current time into the table below without stopping the clock — useful for timing laps, rounds, or stages. Reset (or the R key) clears everything back to zero.

What do the keyboard shortcuts do?

• Space — start, pause, or resume the clock.
• L — record a split.
• R — reset to zero.

The shortcuts are ignored while you are typing in the threshold box, so entering a number never accidentally starts the timer.

What is a split?

A split (or lap) records two things: the total elapsed time at that instant, and the lap time — how long since the previous split. Timing four laps of a track, for example, gives you the cumulative time at each lap plus each individual lap's duration, so you can see which lap was fastest.

What does the threshold do?

Set a threshold in seconds and any lap slower than that is highlighted in the splits table. Leave it at zero to turn the highlighting off. It is handy for spotting the laps, reps, or stages that ran long at a glance.

Is it accurate?

The elapsed time is measured from your device's clock, not by counting animation frames, so it stays accurate even if the browser tab is in the background or your machine is briefly busy. It displays to the centisecond (1/100th of a second). As with any software stopwatch, the practical limit on precision is your own reaction time when you press start and stop — for anything requiring certified accuracy, use a dedicated timing device.

Does it keep running if I close the tab?

No. The chronometer lives entirely in the page, so closing or reloading the tab clears it. It is designed for quick, in-the-moment timing rather than long-running background tracking.