Is it accurate enough to time a workout or a race?
For anything measured in seconds, yes. It reads the browser's high-resolution clock and accumulates real elapsed time rather than counting ticks. What it will not do is give you the hundredths of a second that a sports timer needs, because the display rounds to whole seconds.
Why did the display freeze and then jump when I came back to the tab?
The browser throttled the timer while the tab was hidden, so the screen stopped refreshing. The elapsed time was still measured from the real clock, so the jump is the display catching up rather than time being invented.
Can I pause and resume?
Yes. The Start button becomes Pause while running, and pressing Start again continues from where you stopped rather than resetting. Reset is a separate button.
What happens if my laptop sleeps?
The tab is suspended along with everything else. When it wakes, the next tick measures the full gap against the real clock, so the elapsed total includes the sleep. If you did not want the sleep counted, pause before you close the lid.
Does it work offline?
Once the page has loaded, yes. It is a few lines of JavaScript running in your tab with no server involved at any point.
How do I start the stopwatch?
Press Start. The count begins immediately and the button becomes Pause. There is nothing to configure first, which is most of the point of a stopwatch.
Is the online stopwatch free?
Yes, with no signup, no ads gating the buttons, and nothing to install. It runs entirely in your browser, and nothing about your timing is sent anywhere.
Does it show milliseconds?
No. Time is accumulated in milliseconds internally, so nothing is lost, but the display rounds down to whole seconds. For splits or reaction-level precision you need a dedicated sports timer.
Can it record laps or splits?
No. Start, pause, resume, and reset are the whole interface. For laps, note the reading at each split and keep the stopwatch running, or use a purpose-built lap timer.
How long can it run?
Indefinitely, as long as the tab stays open. Once the elapsed time passes an hour, the display switches to an hours, minutes, and seconds format. Closing or reloading the tab is the only thing that loses the count.
Can I use it in fullscreen?
There is no dedicated fullscreen button, but the browser's fullscreen mode works: press F11 on Windows or Control plus Command plus F on a Mac. The digits are large and tabular, so the readout is legible at a distance either way.