Stopwatch
Free online stopwatch with lap timing. Millisecond precision, keyboard shortcuts, and an unlimited number of laps. Runs entirely in the browser.
Quick answer
Press start to begin timing. Press lap to record a split without stopping. Press stop to pause; resume to continue from where you left off. The display updates every 10 milliseconds — sub-second timing is reliable for casual use but won't beat a hardware stopwatch for race timing.
Stopwatch
How it works
Tracks elapsed time at 10-millisecond resolution using performance.now(), the browser's high-precision monotonic clock. Lap times are stored in memory only — closing the tab clears them.
When to use it
Timing workouts, cooking steps, productivity sprints, page load tests, or anything where you want elapsed time without committing to a full Pomodoro cycle.
Common mistakes
Confusing this with a countdown timer. A stopwatch counts up from zero with no end; a countdown timer counts down from a target to zero.
How the stopwatch works
The tool uses the browser's high-resolution timestamp clock (performance.now()) which has sub-millisecond precision in most browsers. Display updates every ~16ms (one animation frame) for smooth visuals. Lap recording captures the exact timestamp of each press without interrupting the running clock — laps show both the split (time since last lap) and total elapsed. The clock keeps running across browser tab switches because the underlying timestamp doesn't pause.
When to use it
Timing workouts, intervals, and HIIT sessions. Tracking how long a task actually takes (most are 50-100% longer than your gut estimate). Practicing public speaking — record yourself with a target time. Measuring page load times manually if dev tools aren't available. Cooking timers where the duration isn't fixed (steak, eggs, anything you stop based on doneness).
Common mistakes
- Closing the tab while running. Closing the browser tab loses all unsaved time data. Use a dedicated app for anything mission-critical.
- Trusting browser timing for sub-millisecond accuracy. Browsers cap performance.now() resolution at 1ms or higher to mitigate timing-based attacks. For sub-millisecond work (audio, latency analysis), use specialized tools.
- Forgetting to stop before reset. The reset button clears everything including laps. Stop first if you want to keep the data visible.
Frequently asked questions
How accurate is the online stopwatch?
Accuracy is limited by the browser's timestamp clock (performance.now), which has 1ms resolution in modern browsers. For human-scale timing — workouts, cooking, public speaking — this is more than enough. For race timing or scientific work, use a hardware stopwatch.
Can I record laps?
Yes. Press the lap button while the stopwatch is running to record a split. Each lap shows both the split time (time since the last lap) and total elapsed. There is no preset lap limit.
Does the stopwatch keep running if I switch tabs?
Yes. The timing is based on the browser's clock, not on visible animation, so background tabs continue counting accurately. The display catches up when you return to the tab.