Free Online Stopwatch
Time anything with a millisecond stopwatch. Record laps with split and total times, use keyboard shortcuts and export laps to CSV.
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How to time laps and splits with an online stopwatch
Start the stopwatch, record laps while it runs and review each lap time next to the running total. Export the lap table as a CSV file when you finish.
- Press Start, or press Space when no button or field is focused.
- Press Lap, or the L key, each time you want to record a split.
- Press Stop to pause and Resume to continue from the same time.
- Review the lap table, where the fastest and slowest laps are marked.
- Choose Export CSV or Copy laps to keep the results, then press Reset, or R, to clear.
When an online stopwatch is handy
A browser stopwatch is useful whenever you need to time something without reaching for your phone. Runners and swimmers can time intervals on a laptop at the track, teachers can time presentations or quiz rounds, and cooks can time steps that do not need an alarm. Developers and testers also use a stopwatch to measure how long a process or page load takes by eye.
Laps are what make a stopwatch more than a clock. Each press of Lap records the time since the previous lap and the total time since you started, so you can compare consistency across repeats instead of only seeing the final number.
Because the lap table can be exported as a CSV file, you can move the results into a spreadsheet for averages, charts or training logs.
Worked example: three running laps
Suppose you start the stopwatch and press Lap at 1:02.350, again at 2:01.900 and once more at 3:05.125. The first lap time equals its total, 01:02.350. The second lap is 2:01.900 minus 1:02.350, which is 00:59.550. The third lap is 3:05.125 minus 2:01.900, which is 01:03.225.
The table marks lap 2 as the fastest and lap 3 as the slowest. In the exported CSV, the second row reads 2,00:59.550,02:01.900,59550,121900, giving both readable times and raw milliseconds so spreadsheet formulas can work with the numbers directly.
How the stopwatch keeps accurate time
Many simple timers add a fixed amount on every tick, which drifts when the browser slows timers in background tabs. This stopwatch stores the moment you pressed Start using performance.now, the browser's monotonic high resolution clock. The display always shows banked time plus the difference between now and the start moment, so it is correct the instant you look at it.
When you press Stop, the elapsed time is added to a banked total and Resume starts a new segment. Laps are calculated the same way, so each split is the total at that moment minus the previous lap's total. The screen refreshes about as fast as your display, typically 60 times a second, so the last digit changes in jumps, but the recorded lap values keep full millisecond detail.
On some devices the high resolution clock can pause while the computer sleeps, so avoid timing across a sleep or lid close.
Common stopwatch mistakes
Pressing Space while a button is focused can trigger that button instead of the shortcut, which is why shortcuts are ignored in that case. Click an empty part of the page first if shortcuts seem not to respond.
Reloading the page, closing the tab or pressing Reset clears every lap, so export or copy the table first. Also remember that human reaction time adds roughly a fifth of a second to manual timing, so very close results may be within that margin rather than a real difference.
Useful tips and limitations
- Click an empty area of the page before using keyboard shortcuts, since shortcuts are ignored while a button or field has focus.
- Export your laps before reloading, because the stopwatch and lap table are not saved.
- Use the CSV export to calculate average lap times in a spreadsheet.
- For close comparisons, have the same person press the button for every run.
Common questions
Does the Online Stopwatch keep running in a background tab?
Yes. Elapsed time is calculated from clock timestamps rather than counted tick by tick, so throttled background tabs still show the correct time when you return.
What keyboard shortcuts does the Online Stopwatch support?
Space starts and stops, L records a lap and R resets. Shortcuts are ignored while you are typing in a field or a button has focus.
How precise is the Online Stopwatch?
It reads the browser's high resolution clock and records laps to the millisecond. Your own reaction time when pressing a button is usually far larger than the clock's error.
Can I export Online Stopwatch laps to Excel or Google Sheets?
Yes. Export CSV downloads a file with lap number, lap time, total time and both values in milliseconds, which opens in Excel, Google Sheets and other spreadsheet apps.
Why does the Online Stopwatch reset when I reload the page?
The stopwatch keeps its state only in the open page and does not save anything to your device. Export or copy your laps before reloading or closing the tab.
How many laps can the Online Stopwatch record?
Up to 1,000 laps per session. The Lap button is disabled once that limit is reached, and the full table can still be exported.
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