How precise is this stopwatch?

The display updates using requestAnimationFrame and shows centiseconds (1/100 of a second). Timing uses Date.now() deltas, which are accurate to ~1–5 ms in most browsers. This is more than sufficient for most activities; for scientific precision, use dedicated hardware.

Does the stopwatch keep running in a background tab?

The display may not refresh when the tab is hidden, but the elapsed time is computed from wall-clock deltas (Date.now()), not interval ticks. When you bring the tab back to the foreground, the display jumps to the correct time.

How do I record laps?

Click the "Lap" button while the stopwatch is running. Each lap records both the split time (time since the last lap) and the cumulative total. The fastest lap is highlighted in green, the slowest in red.

Can I export my lap times?

Yes. Click "Export CSV" above the lap table to download a CSV file with lap number, split time, and total time for each lap.

Does it work on mobile?

Yes, the stopwatch is fully responsive. Tap Start, Lap, and Reset just as you would on a desktop.

Stopwatch - Free Online Stopwatch with Lap Timer

Free online stopwatch with lap timer

This stopwatch measures elapsed time with centisecond precision, right in your browser. No download, no sign-up. Hit Start, record laps, stop, and export your splits as a CSV file.

How to read the lap table

Each row in the lap table shows three values:

Lap: the sequential lap number.
Split: the time elapsed between the previous lap and this one.
Total: the cumulative elapsed time at the moment this lap was recorded.

The fastest split is highlighted in green (Best); the slowest in red (Worst). These labels appear once you have two or more laps.

Exporting laps to a spreadsheet

Click Export CSV to download a .csv file compatible with Excel, Google Sheets, and Numbers. Each row contains the lap number, split time, and total time in MM:SS.cc format (or HH:MM:SS.cc for runs over one hour).

Stopwatch precision explained

Timing is based on Date.now() deltas rather than setInterval ticks, so the elapsed time stays accurate even when the browser tab is hidden or JavaScript execution is throttled. The display refreshes via requestAnimationFrame for smooth centisecond updates while the tab is active.

Common uses

Running and cycling: lap times for each mile or kilometer.
Swimming: split times per length or per 100 meters.
Cooking: time cooking stages.
Presentations: practice keeping within a time limit per section.
Coding sessions: rough time-on-task without a dedicated app.

Keyboard shortcuts

Space: start or stop the stopwatch
Enter: record a lap (while running)
Delete / Backspace: reset (while stopped)

Accuracy vs. dedicated sports timers

Browser-based stopwatches have inherent timing limitations:

JavaScript timers can be throttled when the tab is not focused or the device is under CPU load. This tool compensates by using Date.now() delta timing rather than accumulating setInterval ticks, but display updates may still lag slightly.
Typical browser stopwatch latency is on the order of 50–150 ms from button press to recorded time - acceptable for most training and coaching uses.
Dedicated electronic sports timers (track starter systems, competitive swimming systems) achieve latency under 5 ms and are required for official competition timing. Use this tool for training, practice sessions, and informal timing.