A precise stopwatch with lap and split times, best and worst lap highlights and CSV export. It runs in your browser and keeps counting through a refresh.
Online Stopwatch
A precise stopwatch with lap and split times, best and worst lap highlights and CSV export. It runs in your browser and keeps counting through a refresh.
Every lap and the stopwatch state stay in this browser. They are saved locally so a refresh does not lose them, and nothing is sent to ArrayKit.
The Online Stopwatch works out elapsed time from timestamps instead of counting timer ticks, so the reading stays correct even when the browser throttles a tab that is in the background. Press Start, Stop and Lap with the buttons or with Space, L and R. Every lap is stored twice: as a lap time, the time since the previous lap, and as a split, the running total. From the third lap the fastest and slowest laps are highlighted and each lap shows how far it sits from your average. The watch is saved whenever it changes, so a refresh or an accidental close does not lose a running session. Copy the laps as text or download them as CSV. Nothing you time leaves your device.
Features
Readout to the hundredth of a second, switching to hours from 59:59, with the hundredths hidden on request
Lap time and split time for every lap, newest first, in a table that scrolls instead of growing
Best and worst laps highlighted from the third lap, with each lap's difference from your average
Summary of lap count, best, worst, average and total time
Keyboard control: Space starts and stops, L records a lap, R resets
A running stopwatch survives a refresh or an accidental close and carries on from its start time
Full-screen mode for a wall display, the live time in the tab title, and, where the browser allows it, the screen kept awake while it runs
Copy the laps as aligned text or download a CSV file for a spreadsheet
How to use the Stopwatch
Press Start, or hit the space bar
Press Lap, or L, each time you pass a checkpoint; the watch keeps running underneath
Press Stop to freeze the time. Resume continues from where it stopped, and Reset clears everything
Read the lap table, then copy it or download the CSV
Example
Input
Start
Lap at 0:10.42
Lap at 0:22.90
Lap at 0:31.15
Stop
Output
Lap Lap time Split time
1 00:10.42 00:10.42
2 00:12.48 00:22.90 worst
3 00:08.25 00:31.15 best
Laps: 3 · Best: #3 (00:08.25) · Worst: #2 (00:12.48) · Average: 00:10.38 · Total: 00:31.15
Lap 3 is the best because it took the least time since the lap before it, not because it has the lowest split.
Common errors & troubleshooting
The Lap button is greyed out. — Laps can only be recorded while the watch is running. Press Start or Resume first; a stopped watch ignores Lap.
Space pressed the wrong button instead of starting the watch. — When a button has keyboard focus, Space presses that button. Click an empty part of the page and Space will start and stop the watch again.
The laps are gone. — Reset clears the laps, so copy them or download the CSV first. The saved stopwatch lives in this browser only, so another browser or cleared site data starts fresh.
The time jumped after the computer woke up. — Time is measured from the moment you pressed Start, so a laptop that slept while the watch was running still counts that time. Stop the watch before closing the lid if you do not want it included.
Frequently asked questions
How accurate is the Online Stopwatch when the tab is in the background?
The measurement stays correct. The reading is calculated from the time you pressed Start, so when the browser slows a hidden tab the display simply catches up to the true elapsed time the next time it updates. What a background tab can lose is how often the display and tab title refresh, not the time itself.
What is the difference between a lap time and a split time?
A lap time is how long one lap took, measured from the previous lap press. A split time is the total elapsed since the start at the moment you pressed Lap. With laps of 10.42 s and 12.48 s the second split is 22.90 s.
Will the stopwatch keep running if I refresh the page or close the tab?
Yes. The state is saved in this browser whenever you start, stop, lap or reset, and a running watch is rebuilt from its original start time when you come back, so the elapsed time includes the time the page was closed. Clear site data or switch browsers and you will see a fresh stopwatch.
How do I export my laps from the stopwatch?
Copy puts an aligned text table with a summary line on the clipboard, and CSV downloads a file with the columns Lap, Lap time and Split time that opens in any spreadsheet. Both include every lap, even when the on-screen table shows only the newest thousand.
Which keyboard shortcuts does the Online Stopwatch support?
Space starts and stops, L records a lap while the watch is running, and R resets it once it is stopped. The shortcuts are ignored while you type in a text box, and Ctrl or Command combinations are left to the browser.
How precise can a browser stopwatch be?
The clock it reads has millisecond resolution and the display shows hundredths of a second, which is finer than a person pressing a button can be, since reaction time adds roughly a tenth of a second or more. It suits timing by hand, such as races, workouts and presentations, rather than laboratory measurements.
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