How to use the online stopwatch
- Press Start or the space bar to begin timing.
- Press Lap (or L) to record split times without stopping. The fastest lap is shown in green and the slowest in red.
- Press Stop to pause and Resume to continue, or Reset (R) to clear.
- Copy the laps or download them as a CSV file for a spreadsheet.
Accurate timing in the browser
The stopwatch measures time with the browser's high-resolution clock and displays hundredths of a second. It calculates elapsed time from the moment you pressed Start rather than counting ticks, so it stays accurate even when the tab is in the background or the device is busy. The state is saved in your browser, so a running stopwatch keeps going if you accidentally reload or close and reopen the page.
Use it for workouts and interval running, timing speeches and presentations, cooking, science experiments, board games, speedcubing practice or measuring how long tasks really take. For counting down from a set time, use the online timer instead. Remember that human reaction time adds roughly 0.1–0.25 seconds to start and stop presses, which matters more than the display precision for very short events.
Does the stopwatch keep running if I close the tab?
The start time is saved, so when you reopen the page, the elapsed time is correct.
How many laps can I record?
As many as you like.
How accurate is it?
The clock is accurate to well under a millisecond; your finger is the limiting factor.