Elapsed time does not depend on repaint ticks
A browser may slow or stop visual updates when a tab is hidden. This stopwatch stores the monotonic start value from performance.now() and derives the total elapsed duration whenever the screen updates again.
Changing the device wall clock cannot move this stopwatch backward or forward. The hundredths place is display precision, not a claim of laboratory timing accuracy.
What it measures
Monotonic elapsed time
Missed browser repaints do not subtract time from an active run.
Split and total laps
Every lap records time since the previous lap and the complete elapsed total.
Running tab title
The elapsed value stays readable in the tab title while the stopwatch runs.
Read split and total lap times
Split is the time since the previous lap, or since Start for lap one. Total is the full elapsed duration at that lap. New laps appear first so the latest result stays close to the controls.
How to use the stopwatch
Press Start
Use the button or Space key to begin.
Record a lap
Use Lap or the L key while the stopwatch is running.
Pause and resume
Stop temporarily without losing elapsed time or laps.
Reset
Use the button or R key to clear the current in-page session.
What the browser can and cannot keep
The screen stays awake while the stopwatch runs when the browser and device support wake lock. The elapsed value also appears in the tab title while running. Both features are progressive enhancements; timing and lap controls still work without them.
The stopwatch keeps its state only in this page. Reloading or closing the tab clears the elapsed time and laps. It does not save a history, sync to an account, or continue after the page is closed.
Frequently asked questions
Does the stopwatch keep running in another tab?
Yes, while this page remains open. Browser throttling can make the visible number update less often, but the next repaint derives elapsed time from the monotonic clock.
Why can I not record a lap while paused?
A lap marks a point in an active run. Resume before recording the next lap.
Does it save my lap history?
No. Laps stay in memory for the current page session and clear on reload.
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