Stopwatch

Online stopwatch with laps, fastest and slowest lap, keyboard shortcuts, full screen and CSV export. Keeps time in background tabs.

How to use

Press Start, or Space on a keyboard. The time shows minutes, seconds and hundredths, and hours once it passes 60 minutes. Pause stops it without losing time, Resume carries on, and Reset sets it back to zero. Lap records the time at that moment: the table shows each lap’s own time and the running total, marks the fastest and the slowest lap, and gives the average.

Keyboard shortcuts: Space starts and pauses, L records a lap, R resets and F switches to full screen. They work anywhere on the page except while typing in a field; when a button has the focus, Space presses that button, as usual. Full screen shows the time in large digits, to read across a room; on iPhone, where pages cannot go full screen, the stopwatch fills the window instead. With Keep the screen on ticked, a phone or laptop does not dim or lock while the stopwatch runs. This uses the Screen Wake Lock API: Chrome and Edge, Firefox 126 and later, Safari 16.4 and later, and Safari on iPhone and iPad from iOS 18.4; where it is missing, the option is not shown.

The time is not counted in ticks: the stopwatch notes the moment you pressed Start and works the time out from the clock each time it draws. A browser that slows down a background tab, or a laptop that sleeps, therefore cannot make it lose time. The tab title shows the running time, so you can follow it from another tab. The stopwatch, its laps and any pause are kept on this device, so a reload or closing the tab does not stop it; Reset clears them.

Download CSV saves the laps for a spreadsheet: lap number, lap time, total time, and both again in seconds. In English the file uses commas and decimal points; in the other languages, semicolons and decimal commas, which is what spreadsheet programs expect there. Copy laps copies the same table as plain text. Nothing is sent anywhere.

Example

Three laps of 1:02.40, 0:58.15 and 1:05.90Totals 01:02.40, 02:00.55 and 03:06.45. Lap 2 is marked fastest, lap 3 slowest, and the average is 01:02.15.
Started at 10:00, paused from 10:05 to 10:07, read at 10:1210:00.00: the two paused minutes are left out.
1 hour, 2 minutes and 3.456 seconds1:02:03.45: hours appear after 60 minutes, and hundredths are cut, not rounded.
Left running in a background tab for 20 minutes20:00.00 when you come back: the time comes from the clock, not from ticks the browser may have delayed.

Frequently asked questions

How precise is it?

The display shows hundredths of a second, and the time is taken from the computer’s clock in milliseconds. In practice the limit is your own reaction time when you press the button, usually a few tenths of a second.

Does it keep running if I switch tabs or close the page?

Yes. It stores the moment it started, so it is right whenever you come back, even after a reload or a browser restart on the same device. A private window forgets it when closed. Reset clears it.

Why does the title update slowly in another tab?

Browsers run hidden tabs less often to save battery; Chrome, after five minutes in the background, about once a minute. The time itself is never affected, and the display is right the moment you come back.

What is the difference between lap time and total?

Lap time is the time since the previous lap, or since Start for the first one; total is the time since Start. A runner’s time at each kilometre is a total, and the time for each kilometre is a lap time.

Can I use it on a phone?

Yes. Tick Keep the screen on so the phone does not lock while it runs, and use Full screen for large digits.