Stopwatch
Start, stop and record laps, with the keyboard if you like. Times are shown to a hundredth of a second.
Runs entirely in your browser
Keyboard: Space start or stop, L lap, R reset. These work when no field or button has focus.
Laps
| Lap | Lap time | Split | Note |
|---|
The display shows hours, minutes, seconds and hundredths and works up to 99 hours. Laps are kept only while the page is open, so download or copy them before closing the tab.
How to use the stopwatch
- Press Start, or tap Space. Press it again to stop; Resume carries on from where you left off.
- While it runs, press Lap or L to record a lap. Each row shows the lap time and the running split.
- Copy the laps or download them as a CSV file for a spreadsheet. Reset or R clears everything.
Lap times, split times and how a browser stopwatch measures them
A stopwatch records two numbers every time you press Lap. The split is the whole time since you started. The lap time is the split minus the previous split. Runners and swimmers read lap times to see whether they are fading; people timing a process, such as steps in a recipe or rounds in a meeting, usually want the splits. Showing both lets you check one against the other: the lap times add up to the latest split.
The page records the browser's monotonic clock when you press Start and again whenever it redraws, and shows the difference. It never adds up "ticks", which is why the number stays right when the browser slows down a background tab, and why pausing and resuming does not lose time: the time before a stop is stored and the new run adds to it. The monotonic clock cannot jump when your computer adjusts its time or changes daylight-saving time.
Lap times are kept in hundredths of a second as whole numbers. That avoids the rounding trap where the rounded laps of 1.234 and 2.345 seconds add up to something different from the rounded total, so what you see always sums.
Tips
- For a time limit that counts down and rings, use the countdown timer.
- Turn the exported times into plain seconds or dates with the Unix timestamp converter.
- Need a fair order of play before the clock starts? Draw one with the random name picker.
Questions
What is the difference between a lap time and a split time?
A lap time is how long that lap took on its own. A split time is the total time on the clock when you pressed Lap. Lap 3 at a split of 3:10.00 with laps of 1:00, 1:05 and 1:05 are the same story told two ways.
How accurate is it?
It reads the browser's high-resolution clock when you press a button and again when it redraws, and shows the difference to a hundredth of a second. Your own reaction time, about a tenth of a second or more, is the larger error. Timing a sport for records needs proper timing equipment.
Does it keep counting if I switch tabs or lock my phone?
It keeps measuring because it works from the clock, not from a count of redraws, so the right time appears as soon as you return. If a phone fully suspends the browser the clock still advances, but you cannot press Lap in the meantime.
Which keyboard shortcuts are there?
Space starts and stops, L records a lap and R resets. They are ignored while you are typing in a field or when a button has focus, so they never fight with normal keyboard use; click on an empty part of the page to use them.
How are the fastest and slowest laps chosen?
Once there are at least two laps, the shortest lap time is labelled Fastest and the longest Slowest, in words as well as colour. If every lap is equal nothing is marked. The lap you are still running is not counted.
What does the CSV contain?
A header row, then one row per lap with the lap number, the lap time and the split time, in hh:mm:ss.cc format. Spreadsheet programs open it directly. Nothing is uploaded: the file is made in your browser.