BYTETOOLS

Online Stopwatch

A precise online stopwatch with lap splits, fastest and slowest lap highlighting, keyboard shortcuts and CSV download of the whole lap table.

00:00.00

Keyboard: space to start or stop, L to record a lap, R to reset.

What is the Online Stopwatch?

The ByteTools Online Stopwatch times anything to hundredths of a second and records lap splits as you go.

  • Hundredth-of-a-second precision from a monotonic clock
  • Unlimited lap splits with cumulative times
  • Fastest, slowest and average lap highlighted automatically
  • Space to start or stop, L to lap, R to reset
  • Copy the lap table or download it as CSV
  • Works offline once the page has loaded

How to use the Online Stopwatch

  1. 1

    Press Start, or hit the space bar, to begin timing.

  2. 2

    Press Lap to record a split without stopping the clock.

  3. 3

    Press Stop to pause, then Start again to resume from where you left off.

  4. 4

    Read the lap table for split times, cumulative times and the fastest and slowest laps.

  5. 5

    Copy the laps or download them as a CSV file, then press Reset to clear.

About the Online Stopwatch

The ByteTools Online Stopwatch times anything to hundredths of a second and records lap splits as you go. Start, stop, resume and reset with the buttons or the keyboard, and every lap is logged with both its own split time and the cumulative elapsed time at that point.

The lap table highlights your fastest and slowest laps and shows the average, which is what makes it useful for interval training, swim sets, cooking stages, lab work, presentation rehearsals and race timing. The whole table can be copied or downloaded as CSV for a spreadsheet.

Timing uses the browser's high-resolution monotonic clock rather than the wall clock, so it cannot be thrown off by a system clock adjustment mid-session. Everything runs locally in your browser with no account and no upload.

Frequently asked questions

How accurate is an online stopwatch?

The timing itself is accurate to well under a millisecond because it uses the browser's high-resolution monotonic clock. In practice your own reaction time on the start and stop buttons — typically 150 to 250 milliseconds — is far larger than any error in the stopwatch.

What is the difference between a lap and a split?

A lap is the time for one segment on its own, while a split is the total elapsed time at that point. This stopwatch records both for every press, so you can see that lap 3 took 1:02 and that you were at 3:15 overall when it ended.

Does the stopwatch keep running if I minimise the window?

Yes. Elapsed time is measured from timestamps rather than counted frame by frame, so the display may pause visually in a throttled background tab but the recorded time stays correct when you come back.

Can I export my lap times?

Yes. Copy the table to the clipboard or download it as a CSV file with lap number, split time and cumulative time as separate columns, ready to open in a spreadsheet for analysis.

Does resetting lose my laps?

Reset clears the clock and the lap table together so the next session starts clean. Copy or download the laps first if you want to keep them, since nothing is stored on a server.

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