How accurate is this browser stopwatch?

It reads from performance.now(), the browser's high-resolution timer, and repaints on every animation frame, so displayed centisecond values are limited mainly by your screen's refresh rate, not by timer drift.

Does a lap show the split time or the total elapsed time?

Each lap records the total elapsed time at the moment you clicked Lap, so to find how long that segment took you subtract it from the lap recorded immediately before it.

Can I resume the stopwatch after stopping it?

Yes, clicking Start again after Stop continues counting up from the elapsed time shown, it does not restart from zero; only clicking Reset clears the elapsed time and lap list.

Does the stopwatch keep running if I switch tabs?

The count is based on the real system clock, not elapsed frames, so the displayed time is correct when you return even if the browser throttled animation frames while the tab was in the background.

Chronometer

A simple stopwatch with laps, running locally in your browser.

Local, Runs entirely in your browser, your data never leaves your device.

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A stopwatch with laps for timing anything in the browser

This is a plain stopwatch: press Start and it counts up in hours, minutes, seconds and centiseconds, press Lap to record the current time without stopping, and Stop pauses the count so you can read it or resume later. It is useful for timing a build, a manual test run, or anything else you'd otherwise time with your phone. The clock is driven by the browser's own timer, so no timing data is sent anywhere.

How to use the Chronometer

Click Start to begin counting from the current elapsed time.
Click Lap while running to record a split without pausing the clock.
Click Stop to pause the count; the display holds the last elapsed value.
Click Start again to resume from where you stopped, rather than from zero.
Click Reset to clear both the elapsed time and the list of recorded laps.

Elapsed time displays as HH:MM:SS.cs, where cs is centiseconds (hundredths of a second), and the clock is driven by requestAnimationFrame against the browser's high-resolution timer rather than a fixed interval.

Laps are listed newest first, each showing the total elapsed time at the moment you clicked Lap, not the duration since the previous lap, so read consecutive laps' difference to get a split time.

Frequently asked questions

How accurate is this browser stopwatch?: It reads from performance.now(), the browser's high-resolution timer, and repaints on every animation frame, so displayed centisecond values are limited mainly by your screen's refresh rate, not by timer drift.
Does a lap show the split time or the total elapsed time?: Each lap records the total elapsed time at the moment you clicked Lap, so to find how long that segment took you subtract it from the lap recorded immediately before it.
Can I resume the stopwatch after stopping it?: Yes, clicking Start again after Stop continues counting up from the elapsed time shown, it does not restart from zero; only clicking Reset clears the elapsed time and lap list.
Does the stopwatch keep running if I switch tabs?: The count is based on the real system clock, not elapsed frames, so the displayed time is correct when you return even if the browser throttled animation frames while the tab was in the background.