Online Stopwatch
Millisecond precision with lap times, keyboard shortcuts, and statistics.
How to Use This Stopwatch
Start and stop with the green Start button or by pressing Space. The stopwatch uses absolute timestamps, so it stays accurate even when the browser tab is in the background or your device briefly lags.
Record laps by clicking Lap or pressing L while the stopwatch is running. Each lap records the total elapsed time and the interval since the previous lap. After two or more laps, your best (fastest) lap is highlighted green and worst (slowest) is highlighted red, with statistics shown above the table.
Export your results using the Copy button (copies to clipboard as tab-separated text, perfect for spreadsheets) or the Download button (saves a .txt file). Both formats include lap number, interval time, and cumulative total.
Fullscreen mode expands the stopwatch to fill your screen — ideal for presentations, coaching, or when you need to see the time from a distance. Press F or click the Fullscreen button.
Session recovery: the stopwatch periodically saves its state to your browser. If you accidentally close the tab and come back, a restore prompt lets you pick up exactly where you left off — elapsed time is recalculated from the original start timestamp, so no time is lost.
Stopwatch vs Timer
| Feature | Stopwatch | Timer |
|---|---|---|
| Direction | Counts up from 0:00 | Counts down to 0:00 |
| Purpose | Measure how long something takes | Wait for a specific duration |
| Alarm | No alarm needed | Alarm when finished |
| Lap times | Yes, with best/worst/avg stats | No |
| Common uses | Racing, workouts, cooking, experiments | Cooking, Pomodoro, study breaks |
Frequently Asked Questions
How accurate is this online stopwatch?
The stopwatch uses Date.now() for timing, providing millisecond-level precision. Because it tracks absolute timestamps rather than counting intervals, the elapsed time stays accurate even when the browser throttles background tab updates. Display refresh uses requestAnimationFrame for smooth 60fps updates.
Does the stopwatch keep running in background tabs?
Yes. The timing is based on absolute timestamps, so even if the display refresh slows down in a background tab, the elapsed time is always correct when you return. The browser tab title also updates with the current time so you can monitor it at a glance.
What happens if I accidentally close the page?
The stopwatch saves its state (elapsed time, running status, and all laps) to your browser's local storage every 2 seconds. When you return to the page, a restore banner appears. If the stopwatch was still running, the elapsed time is calculated from the original start time, so no time is lost.
What do the green and red highlights mean?
Green indicates your fastest (best) lap interval — the shortest time between two lap marks. Red indicates your slowest (worst) lap interval. These highlights appear automatically once you've recorded at least two laps. The summary bar above the table shows best, average, and worst interval times at a glance.
How do I export my lap times?
Two options: click Copy to place all lap data on your clipboard as tab-separated text (pastes cleanly into Excel, Google Sheets, or any text editor), or click Download to save a .txt file. Both include lap number, interval time, and cumulative total time.
What keyboard shortcuts are available?
Space starts or stops the stopwatch, L records a lap while running, R resets when stopped, and F toggles fullscreen mode. These work unless you are focused on a text input.