Online Stopwatch
A precise, free online stopwatch with lap times. Start, pause, resume and record laps with millisecond accuracy — it runs entirely in your browser.
Keyboard shortcuts: Space start / pause · L lap · R reset
Laps
| Lap | Lap time | Total time |
|---|
How to use the online stopwatch
- Start the timer. Click Start or press the Space bar. The display counts up with millisecond precision.
- Record laps. While the stopwatch is running, click Lap (or press L) to mark a split. Each row shows the lap time and the running total, with the fastest lap in green and the slowest in red.
- Pause, resume or reset. Space toggles pause and resume without losing time. When you're done, copy the lap list or download it as a CSV file, then press Reset to start over.
About this tool
This free online stopwatch measures elapsed time with millisecond resolution using your browser's high-precision monotonic clock (performance.now), which keeps counting accurately even while the tab is in the background or your system clock changes. That makes it reliable for timing workouts, HIIT intervals, running and swimming laps, cooking, speedcubing, presentations, exams and lab experiments — no app install or sign-up needed.
Lap support turns it into a split timer: every lap records both the individual segment time and the cumulative total, and the fastest and slowest laps are highlighted automatically. Everything runs locally in your browser and nothing is sent to a server; note that the timer resets if you close or reload the page, so export your laps before leaving.
Frequently asked questions
How accurate is this stopwatch?
It reads the browser's monotonic high-resolution timer rather than the wall clock, so it is typically accurate to about a millisecond and is unaffected by system clock adjustments. Browsers may round the timer slightly (often to 0.1 ms or 1 ms) as a privacy measure, which is negligible for everyday timing.
Does it keep running if I switch tabs or minimize the window?
Yes. The elapsed time is computed from timestamps, not from screen updates, so when you come back the display catches up to the correct time instantly — even if the browser paused animations while the tab was hidden.
What is the difference between lap time and total time?
Total time is the overall elapsed time when you pressed Lap. Lap time is the time since the previous lap (or since the start, for lap 1). The lap times always add up to the last total.
Can I save my lap times?
Yes — use Copy laps to put the list on your clipboard as text, or Download CSV to save a spreadsheet-ready file with lap numbers, lap times and totals in both readable and millisecond form.