How to use the stopwatch
Press Start or the Space bar and the stopwatch starts counting in minutes, seconds and thousandths of a second; after an hour it adds an hours column. Press Lap or L (or Enter) each time a runner crosses the line, a swimmer touches the wall or a machine finishes a cycle. Stop freezes the time without losing anything — press Start again to resume from the same point — and Reset (R) clears it. Reset by mistake? An Undo button appears for twelve seconds.
The line under the main display is the lap currently in progress, so you can see how the current lap compares while it is still running. Use the precision switch in the toolbar to show thousandths, hundredths or tenths; the timing underneath is always recorded to the millisecond whatever you display, and exports always contain full precision.
Full screen (or F, or double-clicking the display) fills the screen with the time and shows your last four laps, which works well on a projector, a gym TV or a tablet propped up at the side of a track.
Lap times, splits and how to read the table
Coaches use the words differently, so here is exactly what each column means:
| Column | Meaning | Example |
|---|---|---|
| Lap time | Time for that lap alone, from the previous lap press to this one | 01:12.480 |
| vs previous | How much slower (+, red) or faster (−, green) this lap was than the one before | −00:01.905 |
| Total (split) | Cumulative time since the start when the lap was pressed — the split | 04:51.022 |
| Clock time | The time of day the lap was taken, useful for logs | 14:03:27 |
Once there are at least two laps, the fastest lap is shaded green and the slowest red, each with a text label so the highlight does not rely on colour. The stats above the table give the lap count, fastest, slowest and average lap. For interval training, a steady average with a small gap between fastest and slowest shows even pacing; a slowest lap near the end usually means the early laps were too fast.
Copy puts a plain-text summary on your clipboard; Export CSV downloads every lap with lap and total times formatted and in raw milliseconds, plus an ISO timestamp, ready for Excel, Numbers or Google Sheets.
How accurate is an online stopwatch?
The stopwatch does not count ticks. It records the high-resolution timestamp of the moment you started and computes the elapsed time from the system clock each time the screen redraws, so it cannot drift, and it carries on correctly when the tab is in the background, the window is minimised or the screen is locked. When you come back, the display is simply right.
The bigger source of error in any stopwatch is the gap between the event and your press. Most web stopwatches start timing when the browser fires the click event, which arrives after you lift your finger — typically 50 to 150 milliseconds late on a touchscreen. This one uses the timestamp of the moment your finger or key went down, which the browser records when the input arrives. What remains is human reaction time, around 150–250 ms for a visual cue; since you react at both start and stop, much of that cancels out, which is why hand timing is generally reliable to about a tenth of a second.
The screen can only show a new number once per refresh (every 16.7 ms at 60 Hz), so the last digit of the millisecond display blurs while running, but the stopped time and lap times are exact to the millisecond.
Several stopwatches, saving and privacy
Timing more than one thing at once — several runners on different starts, parallel experiments, or two tasks you bill separately? Press Add stopwatch. Each stopwatch has its own name (click the name above the display to change it), its own laps and its own export. A tab strip shows every stopwatch with a live time and a green dot when it is running; click one, or press 1–8, to make it the one your keyboard shortcuts control. The others keep running while you work with it.
Everything is saved in your browser's local storage as you go. Reload the page, close the tab or restart the browser and your stopwatches come back exactly where they were — a running stopwatch will have kept counting. Nothing is uploaded or tracked. If you need a countdown instead, use the online timer; for timing a talk against green, amber and red cards, the speech timer is built for it, and a tally counter pairs well for counting reps or laps without timing them.
Frequently asked questions
Does the stopwatch keep running if I switch tabs or lock my phone?
Yes. Time is calculated from the moment you pressed Start using the system's high-resolution clock, so it does not depend on the page being visible. Switch tabs, minimise the browser or lock the screen and the elapsed time is still exact when you return. It even survives reloading or closing the tab, because the start time is saved locally.
How do I record a lap or split time?
Press the Lap button, or L or Enter on the keyboard, while the stopwatch is running. Each press adds a row with the lap time, the difference from the previous lap and the total elapsed time, which is the split. The lap in progress is shown under the main display so you can watch it live.
Can I export my lap times?
Yes. Export CSV downloads every lap with lap and total times in both readable format and raw milliseconds, plus the date and time each lap was recorded. The file opens directly in Excel, Numbers or Google Sheets. Copy puts a plain-text version on your clipboard for pasting into a message or notes.
Is it accurate to the millisecond?
The timing itself is, because it uses the browser's high-resolution clock and the exact timestamp of your key press or tap rather than when a click event fires. What limits accuracy is human reaction time, roughly 0.15–0.25 seconds, and the screen refresh rate while it runs. For hand timing, trust results to about a tenth of a second.
What are the keyboard shortcuts?
Space starts and stops, L or Enter records a lap, R resets (with an Undo button in case you pressed it by accident), and F toggles full screen. With several stopwatches, the number keys 1 to 8 choose which stopwatch the shortcuts control. Shortcuts are ignored while you are typing a stopwatch name.
Can I run more than one stopwatch at once?
Yes, up to eight. Press Add stopwatch and a tab strip appears with each stopwatch's name and live time. They run independently, each with its own laps and export, and you can remove one with the cross on its tab. All of them are saved if you reload the page.