Stopwatch
A precise stopwatch with lap tracking — press Space to start and stop, L to record a lap.
00:00.00
minutes : seconds . hundredths
Keyboard: Space start / pause, L lap
How it works
- Click Start, or press the Space key, to begin timing.
- Press Lap (or the L key) while running to record split times — the fastest and slowest laps are marked in the list.
- Click Pause to stop the clock without losing the time, or Reset to clear everything and start over.
Frequently asked questions
- How accurate is this online stopwatch?
- Timing is based on the browser’s high-resolution performance clock, the same monotonic timer used for performance measurement, so accumulated error is negligible over hours. The display refreshes every screen frame and shows hundredths of a second, which is finer than human reaction time of roughly 150–250 milliseconds.
- Does the stopwatch keep running if I switch tabs?
- Yes. The elapsed time is calculated from timestamps, not from counting ticks, so the total stays correct even when the browser pauses background animation to save power. When you return to the tab, the display immediately shows the true elapsed time.
- What do the lap and total columns mean?
- Each lap row shows two numbers: the lap time, which is the interval since the previous lap, and the total, which is the overall elapsed time when you pressed Lap. This matches how physical sports stopwatches record splits, so you can read both per-interval pace and cumulative time at a glance.
- Is anything uploaded or tracked while I use it?
- No. The stopwatch is plain code running locally in your browser — it makes no network requests, stores nothing, and works offline once the page has loaded. Closing the tab discards the session completely.
- What can I use a stopwatch with laps for?
- Lap timing suits anything with repeated intervals: track and swim training, interval workouts like HIIT sets, timing exam sections, speedcubing, board-game turns, or measuring repeated steps in a manual process. Recording splits rather than restarting the clock keeps the overall total intact while still capturing each segment.
About this tool
A stopwatch measures elapsed time from a starting point you choose, and adding laps makes it far more useful than a bare counter: you capture the length of each interval without interrupting the overall measurement. This one shows minutes, seconds and hundredths in a large monospace display, records unlimited laps, and highlights your fastest and slowest splits so patterns stand out immediately — a fading pace in the final intervals of a workout, or one outlier step in a repeated task.
Under the hood the timer reads the browser’s high-resolution performance clock, a monotonic timer that is unaffected by system clock changes and precise to fractions of a millisecond. Rather than counting ticks, the stopwatch stores the moment you pressed Start and computes the difference on every screen frame, so the display stays smooth and the total cannot drift, even during long sessions or while the tab is in the background. Everything runs locally in your browser: no network requests, no account, nothing stored anywhere.
Keyboard control matters when your attention is elsewhere. Space starts and pauses the clock, and L records a lap, so you can time laps at a track meet or splits in a practice session without looking away to find a button. On a phone, the large buttons serve the same purpose — each control is big enough to hit reliably mid-activity.
A few practical notes. Human reaction time adds roughly two tenths of a second at start and stop, so for short measurements treat the hundredths digit as indicative rather than exact. For interval training, press Lap at each transition instead of resetting — you keep the session total and get every segment. And since the page works offline after loading, it is dependable in gyms and sports halls with poor reception.