Online stopwatch
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Ready
Start it and read the time that has passed. While this page stays open, the running count follows the browser's monotonic clock, so changing the system time does not rewind it. You can use this stopwatch in the browser at no charge.
What this stopwatch is
A stopwatch measures elapsed time. It counts up from zero. It is not a countdown timer, and it does not keep a live measurement after this page is gone.
How to use it
- Press Start. Pause holds the elapsed time, and Resume continues from that point.
- Lap stores the total so far and the time since the previous lap.
- Reset clears the elapsed time and the lap list. Full screen makes the digits easier to see.
What you can do
- Start, pause, resume, and reset.
- Up to 100 laps, each with its own duration and the total elapsed time.
- A full-screen view when the browser allows it.
Ways to use it
- Workouts, speeches, and cooking steps where you need the time spent, not a countdown.
- Comparing laps in a run, a study block, or a repeated task.
Accuracy and browser limits
- While this page stays open, elapsed time is taken from the browser's monotonic clock. A background tab may stop drawing, but the count is not built by adding up screen updates. Coming back shows the time that actually passed.
- A reload cannot reuse the previous monotonic clock. If the stopwatch was running, the gap is estimated from the system clock and then a new monotonic segment starts.
- If you change the system time, or the operating system corrects the clock, that reload estimate can be wrong. The page never treats that estimate as a certified measurement.
- Closing the tab or quitting the browser stops the live measurement. Opening the page later can add the system-clock gap if a running session was saved. That is not the same as the stopwatch keeping time while the browser is closed.
- Clearing site data removes the saved session. This is a web page, not a dedicated timing device.
Questions
What is an online stopwatch?
An online stopwatch counts elapsed time upward from zero. You can pause it, continue, and mark laps.
Is this stopwatch accurate?
While the page stays open, the running time follows the browser's monotonic clock. It is a web page, not a certified timing instrument.
Does the stopwatch keep counting in a background tab?
The elapsed time still follows the monotonic clock if the page has not been destroyed. The browser may pause drawing. When you return, the display catches up to that clock.
What happens if I refresh the page?
A paused stopwatch comes back with the saved elapsed time. A running stopwatch adds the time since it started that segment, using the system clock, and then continues on a new monotonic segment. A system-clock change can skew that restored gap.
What is a lap time?
A lap is a snapshot of the total elapsed time. The lap duration is the difference between that snapshot and the previous one.
Does closing the browser stop the stopwatch?
Yes. The live measurement stops when the page is gone. If you open it again and a running session is still saved, the time you were away is only an estimate from the system clock.