Online stopwatch
Start with Space, record laps with L, export every split as CSV.
00:00.00
Press Esc to exit
Laps
No laps yet. Press Lap, or L, while the stopwatch runs.
| Lap | Split | Total |
|---|
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Press Start, or the space bar, and the stopwatch runs until you stop it. Press L to record a lap, so you can time the parts of a workout, a lab experiment, a rehearsal or a support call and still watch the total climb. Every lap keeps its own split as well as the running total, and the whole list saves as a CSV file for a spreadsheet. The clock is monotonic, so a change to the system time cannot move it, and it keeps counting correctly while the tab sits in the background. Everything happens in this page. Nothing is sent anywhere.
How to use
- Press Start, or the space bar, to begin timing.
- Press Lap, or L, each time you want to mark a split. The list keeps both the split and the running total.
- Press Stop to pause, and Start again to continue from where you left off.
- Use Export CSV to save the laps as a spreadsheet file, or Copy laps to put the same rows on the clipboard.
- Go fullscreen for a face you can read across a room; Esc leaves it. Reset clears the time and the laps.
What it handles
- Runs on a monotonic browser clock, so a system-time change or a daylight saving switch cannot alter the reading.
- Keeps counting in a background tab, and the tab title shows the elapsed minutes and seconds while you work elsewhere.
- Never rounds up: the face shows the time already reached, in hundredths, or in thousandths with the milliseconds option.
- Adds an hours field on its own once a run passes 59:59, in the display, in the lap list and in the export.
- Marks the fastest and the slowest lap in color and in words, as soon as two laps actually differ.
- Records up to 1,000 laps and escapes commas and quotes in the export, so the CSV opens correctly in any spreadsheet.
FAQ
How accurate is an online stopwatch?
It reads a monotonic clock that the browser deliberately coarsens to a fraction of a millisecond to prevent tracking, so the timing is comfortably inside the hundredth of a second the face shows. The bigger error is human: the gap between seeing an event and pressing a key is far larger than anything the clock adds.
Does it keep running when I switch tabs?
Yes. Elapsed time is measured from clock readings, not by counting frames, so a hidden tab cannot fall behind. The face stops repainting while the tab is in the background to save battery, and the tab title still updates about once a second. When you come back, the time shown is the real elapsed time.
Do I lose the laps if I reload the page?
Yes. The stopwatch does not restore itself after a reload, because it would have to guess how long the tab was closed. Export or copy the laps before you leave. Only the milliseconds setting is remembered, on this device alone, and Reset clears the time and the lap list right away.
What is in the CSV file?
Five columns: the lap number, the split, the total, and both times again in whole milliseconds, so you can chart them without parsing the clock format. Headers are written in the language of the page, and a byte-order mark is added so accented and Cyrillic headers open correctly in Excel.
Is there a limit on the number of laps?
Yes, 1,000 laps. Above that the Lap button stops adding rows and says why, because a longer list is no longer readable on a phone. If you need more, export the file, reset, and carry on: a file already saved to your device is not touched by the reset.
Is anything uploaded?
No. The stopwatch runs entirely in your browser and needs no connection once the page has loaded. Nothing is timed, logged or stored on a server. The CSV file is written by your browser and saved straight to your device, so lap times never leave the machine you are on.
Updated