Online Stopwatch
Start, stop and record laps with millisecond precision using your browser's high-resolution performance clock. Fastest lap turns green, slowest turns red, so you can spot trends at a glance. Export the lap list as a spreadsheet-friendly CSV when you're done.
Times stay in your browser. Nothing is uploaded.
How to use this stopwatch
- Click Start to begin. The display updates in real time with millisecond precision.
- Click Lap to record split times — each lap shows its duration and the running total.
- Click Stop to pause, then Start again to resume from where you stopped.
- Copy laps to clipboard or export as CSV with one click.
Frequently asked questions
How precise is the stopwatch?
It uses your browser's high-resolution performance clock, accurate to a millisecond. Display updates every animation frame (~60 fps).
What does Lap do?
Lap records the current elapsed time and starts a new split. Each lap shows its individual duration and the cumulative total.
Are fastest and slowest laps highlighted?
Yes. With two or more laps, the fastest is shown in green and the slowest in red.
Can I export the laps?
Yes. Click Download CSV to save a spreadsheet-friendly file with lap number, lap duration and cumulative total — opens directly in Excel, Google Sheets or Numbers. Or use Copy Laps for a clipboard version you can paste into a doc.
Does the timer keep running if I switch tabs or lock my screen?
Yes. The elapsed time is calculated from timestamps (start time vs. now), not from a counter that increments — so it stays accurate even if the tab is backgrounded, throttled or the screen is locked. The display freezes when the tab is hidden, but the stored start time is correct when you return.
Why is my first lap usually slower than the rest?
Reaction time. The 'start' click takes 200-500ms before your hand finishes the action you're timing. If you're timing yourself, the first lap includes that reaction lag. If you're timing someone else, calling out the start adds even more. Either ignore the first lap or use the cumulative total for accuracy.