Online Stopwatch
A free online stopwatch with start, stop, reset, and lap timing down to centiseconds.
About the Online Stopwatch
The Online Stopwatch is a fast, no-nonsense timer for measuring how long something takes — a workout interval, a cooking step, a study sprint, a phone call, or a quick lap around the track. It shows the elapsed time in a large, easy-to-read display down to the centisecond (hundredths of a second), so you can catch even tight margins. Press Start to begin, Stop to pause, Reset to clear it, and Lap to record split times without interrupting the count. Everything runs directly in your browser, so there is nothing to install and nothing to sign up for.
What sets a good stopwatch apart is accuracy over long runs, and this one is built for it. Rather than naively counting screen refreshes — which can drift by seconds over minutes as the browser throttles or skips frames — it measures elapsed time from real system timestamps and adds up only the periods when the clock was actually running. That means if you start it, pause for lunch, and resume later, the total reflects the true time the stopwatch was active. The lap list captures both the split (time since the previous lap) and the running total at each press, which is exactly what you want for comparing repeated efforts like sprint intervals or recipe stages.
Because it is purely client-side, the stopwatch keeps working even if your connection drops, and none of your timing data ever leaves your device. It is a handy companion for athletes, teachers, cooks, gamers, developers timing a process, or anyone who just needs a reliable clock without the clutter of a full app.
How to use
- Click Start to begin timing. The large display immediately begins counting up in HH:MM:SS.cs.
- Click Lap whenever you want to record a split. Each lap shows both its individual split time and the cumulative total, listed newest-first below the controls.
- Click Stop to pause the stopwatch while keeping the current time on screen. Click Start again to resume from where you left off.
- Click Reset to set the display back to zero and clear all recorded laps. This works whether the stopwatch is running or paused.
- Use Copy laps to copy the full lap list (lap number, split, and total) to your clipboard as plain text you can paste into a note or spreadsheet.
Frequently asked questions
How accurate is this online stopwatch?
The stopwatch computes elapsed time from your device's real clock using timestamp differences, not by counting animation frames or interval ticks. This keeps it accurate even over long sessions or when the browser tab is throttled in the background. It displays down to centiseconds (hundredths of a second), though the practical precision depends on your reaction time when pressing the buttons.
What is the difference between a lap's split and its total?
The total is the full elapsed time from when you first started the stopwatch to the moment you pressed Lap. The split is just the time since your previous lap. For example, in a running workout the split tells you how long each individual lap took, while the total tells you your overall time so far.
Can I pause and resume without losing my time?
Yes. Pressing Stop pauses the count and freezes the display, and pressing Start again continues from that exact point. The stopwatch only accumulates time during periods when it was actually running, so pauses are never counted toward your total.
Does the stopwatch keep running if I switch tabs?
The timing stays correct because it is based on real timestamps rather than frame counting, so when you return to the tab the elapsed value reflects the true time that passed. The on-screen digits update roughly 30 times per second while visible; browsers may slow updates for hidden tabs, but the underlying measurement remains accurate.
Is my timing data sent anywhere or saved?
No. This tool is entirely client-side — all timing and lap tracking happen in your browser, and nothing is uploaded, logged, or stored on a server. Once the page has loaded it even works offline. Note that reloading or closing the page clears the current time and laps, since nothing is persisted.
Why does the time reset when I reload the page?
The stopwatch keeps its state in memory only, which keeps it simple and private. Refreshing the page, navigating away, or closing the tab clears the elapsed time and lap list. If you need to keep a result, use the Copy laps button to save your splits before leaving.