How accurate is this online stopwatch?

It shows hundredths of a second and measures from your device clock: the time is always “now minus the moment you pressed Start”, so it does not drift the way a count of ticks can. What limits accuracy is your reaction time on the button, typically a tenth to a quarter of a second, not the page.

Does the stopwatch keep running in the background or if I close the tab?

Yes. Switching tabs or apps doesn’t pause it, and the display is right the moment you come back. The stopwatch’s state is saved in this browser, so after a reload or reopening the page it is still running (or stopped) with its laps, until you press Reset.

What is the difference between a lap time and a split time?

A lap time is how long that one lap took; a split is the total time from the start to the end of that lap. On a 3-lap run with laps of 1:10, 1:05 and 1:08, the splits are 1:10, 2:15 and 3:23. The table shows both.

How do I copy my laps into a spreadsheet?

Press Copy laps and paste into Google Sheets, Excel or Numbers: each lap lands on its own row with the lap number, lap time and total in separate columns, followed by the total time.

Will it keep my screen on?

Yes, while the stopwatch is running, in browsers that support the Screen Wake Lock API (Chrome, Edge, Safari 16.4 and later, Firefox 126 and later). When it stops, the screen can sleep again.

Can it count down instead?

A stopwatch counts up. To count down from a length of time with an alarm, use the online timer; to count down to a date, use the countdown page. Both are linked below.

Online Stopwatch with Laps

Press Start (or the Space bar) to time anything to the hundredth of a second, and Lap (or L) to record lap times. The lap table shows each lap’s own time and the running total (the split), marks the fastest and slowest lap, and copies as text you can paste into a spreadsheet. The stopwatch keeps counting in a background tab and after a reload.

Updated 2026-09-28Runs in your browser: nothing you enter is uploadedHow this tool works

Ready

00:00.00

Space start/stop ·L lap ·R reset ·F full screen

Laps

No laps yet. Press Lap (or L) while the stopwatch runs to record one.

The stopwatch keeps running in a background tab and after a reload: its state stays in this browser until you press Reset.

Keyboard shortcuts

Shortcuts work whenever you are not typing in a field or on a button.
Key	What it does
Space	Start, stop, or resume the stopwatch
L	Record a lap (while running)
R	Reset to zero and clear the laps
F	Full screen on or off (Esc also leaves full screen)

How to use the stopwatch

Start. Press Start or the Space bar. The time counts up in minutes, seconds and hundredths.
Record laps. Press Lap or L at the end of each lap, round or split. The newest lap appears at the top of the table with its own time and the total so far.
Stop and resume. Press Stop (or Space) to pause the count, and Resume to carry on from the same time.
Copy or reset. Copy laps puts the table on your clipboard as tab-separated text for a spreadsheet or message. Reset (or R) clears the time and the laps.

Frequently asked questions

How accurate is this online stopwatch?: It shows hundredths of a second and measures from your device clock: the time is always “now minus the moment you pressed Start”, so it does not drift the way a count of ticks can. What limits accuracy is your reaction time on the button, typically a tenth to a quarter of a second, not the page.
Does the stopwatch keep running in the background or if I close the tab?: Yes. Switching tabs or apps doesn’t pause it, and the display is right the moment you come back. The stopwatch’s state is saved in this browser, so after a reload or reopening the page it is still running (or stopped) with its laps, until you press Reset.
What is the difference between a lap time and a split time?: A lap time is how long that one lap took; a split is the total time from the start to the end of that lap. On a 3-lap run with laps of 1:10, 1:05 and 1:08, the splits are 1:10, 2:15 and 3:23. The table shows both.
How do I copy my laps into a spreadsheet?: Press Copy laps and paste into Google Sheets, Excel or Numbers: each lap lands on its own row with the lap number, lap time and total in separate columns, followed by the total time.
Will it keep my screen on?: Yes, while the stopwatch is running, in browsers that support the Screen Wake Lock API (Chrome, Edge, Safari 16.4 and later, Firefox 126 and later). When it stops, the screen can sleep again.
Can it count down instead?: A stopwatch counts up. To count down from a length of time with an alarm, use the online timer; to count down to a date, use the countdown page. Both are linked below.

How it works

Pressing Start stores the current time from your device clock; the elapsed time shown is the time stored before plus now minus that start. Stopping adds the run to the stored total. The display is redrawn on each animation frame while the tab is visible (four times a second if your system asks for reduced motion), and a hidden tab doesn’t need redrawing at all, so no time is lost when the browser slows background tabs. Hundredths are rounded down. Laps store the total at each press; a lap’s own time is the difference from the previous lap. The state is kept in this browser’s local storage until Reset and never sent anywhere; anonymous usage statistics record only which button was pressed.

Sources

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