How to use the online stopwatch
- Start: press the Start button or the spacebar. The time runs in minutes, seconds and hundredths, and switches to hours after 60 minutes.
- Record laps: press Lap (or L) each time a lap, a rep or a step ends. The current lap is shown under the main time.
- Stop and resume: press Stop to pause, then Resume to continue from the same time. Reset clears the time and the laps once the stopwatch is stopped.
- Save your laps: Copy laps puts the table on your clipboard as text with tabs, ready to paste into a spreadsheet, email or notes.
Laps, splits and the lap table
Each row shows the lap time (how long that lap took) and the total, also called the split (time since you started). Once you have two or more laps, the fastest lap turns green and the slowest red, so you can see at a glance where you sped up or slowed down. Newest laps sit at the top.
| Use | How to time it |
|---|---|
| Running laps or swimming lengths | Lap at the end of every lap; compare lap times for pacing. |
| Interval workouts | Lap at the end of each work and rest block. |
| Classroom activities and presentations | Full screen on the projector; lap when each group or speaker finishes. |
| Cooking, experiments, tasks | Start once, lap at each step to see what takes longest. |
Need to count down instead of up? The classroom timer runs a countdown with a big visual pie and an end chime.
Why this stopwatch doesn't drift
Many simple web stopwatches add a few milliseconds every time the screen refreshes. Browsers slow those updates down in background tabs, so the time falls behind. This online stopwatch works the other way: it stores the exact moment you pressed Start and always shows the difference to the current time. Background tabs, a sleeping screen or a busy computer can delay the display, but never the result.
The same stored start time lets the stopwatch survive a reload or an accidentally closed tab. Open the page again and it shows the right time, still running, with your laps.
How accurate is it?
The clock is far more precise than you need. The real limit is your thumb: human reaction time adds roughly 0.1–0.25 seconds when you start and stop by hand, which is why official races use electronic timing. If you're curious about your own delay, try the reaction time test. For fair comparisons, have the same person start and stop every attempt.
How we tested this tool
We ran the stopwatch in Chrome and compared it with the browser's own clock: a 3-second run read 3.00 seconds (within 0.02 s), a run with a 2-second pause in the middle excluded the pause, three laps added up exactly to the total, the fastest and slowest laps were marked correctly, the time and laps were restored after a page reload while running, and Space, L and R worked as shortcuts. We also checked that the display caught up correctly after the tab was hidden.
Frequently asked questions
Does the online stopwatch keep running if I switch tabs or lock my screen?
Yes. The time is calculated from the moment you pressed Start, not by counting ticks, so switching tabs, minimizing the browser or locking the screen doesn't slow it down. The display catches up as soon as you come back.
What happens if I close or reload the page?
The stopwatch remembers its start time and laps in your browser, so when you open the page again it shows the correct elapsed time and is still running. Nothing is uploaded; clearing your browser data resets it.
How accurate is a browser stopwatch?
The clock itself is accurate to well under a millisecond, and the display shows hundredths of a second. The limit is human reaction time when pressing the button, which adds about 0.1 to 0.25 seconds at the start and stop. For official race timing use electronic timing gates.
What is the difference between lap time and split time?
Lap time is how long one lap took, from the previous lap press to this one. Split time (shown as Total) is the time since the start. The lap table shows both, and marks the fastest lap in green and the slowest in red.
Can I use the stopwatch with the keyboard?
Yes. Press Space to start and stop, L to record a lap and R to reset when the stopwatch is stopped. The buttons are large enough to use on a phone or tablet too.