How to use the online stopwatch
- Press Start, or press the Space bar, to begin timing. The display counts minutes, seconds and milliseconds.
- Press Lap, or the L key, at each checkpoint. Every lap records a split (time since the previous lap) and a total (time since you started).
- Press Stop to freeze the clock. Resume carries on from the stopped time. Reset returns to zero and clears the laps.
- Use Copy laps to put the table on your clipboard as tab-separated text, or Download CSV to open it in a spreadsheet.
How the stopwatch stays accurate
A common way to build a web stopwatch is to add a fixed amount to a counter every time a timer fires. That drifts, because browsers slow down timers in tabs you cannot see, and a busy page can fire them late. This stopwatch does not count ticks at all. When you press Start it records the browser clock reading at that instant. Whenever it needs to show the time, it subtracts that reading from the current one and adds any time banked from earlier runs.
Because the answer is always a subtraction of two clock readings, the elapsed time is correct no matter how often the screen was redrawn. If you start the stopwatch, switch to another tab for ten minutes and come back, the display jumps straight to the right value. The screen itself is redrawn with the browser animation schedule, which pauses in hidden tabs to save battery. Only the drawing pauses, never the measuring.
The clock used is the monotonic high resolution clock the browser provides for performance measurement. It does not move backward if you change the system date or time zone. Some privacy focused browser settings deliberately round that clock to coarser steps, such as 100 milliseconds. If you see the last digit stuck at zero, that is your browser, not the tool.
Laps, splits and totals
A split is the time for one lap alone. The total is the time from the start to the end of that lap. Suppose you press Lap at 12.340, 25.100 and 37.020 seconds. The totals are those three numbers. The splits are 12.340, then 25.100 minus 12.340 = 12.760, then 37.020 minus 25.100 = 11.920. Lap 3 is the fastest and lap 2 the slowest.
Once you have two or more laps, the fastest and slowest splits get a text tag in the table. The tag is words, not just a color, so it works for everyone. The newest lap is listed first so the latest result stays in view without scrolling.
Keyboard use and screen readers
Press Space to start or stop and L to record a lap. The shortcuts are ignored while you are typing in a text box, and Space is left alone when a button or link has focus, because it already presses that control. Every control is a real button with a visible focus outline and a touch target of at least 44 pixels.
The running time is deliberately not announced to screen readers, because reading out every millisecond would make the page unusable. Instead the tool announces actions: started, stopped at a spoken time, each lap with its split and total, and reset.
Privacy
Nothing you time is stored or sent. The laps exist only in this tab and disappear when you reload or close it. Copy or download them first if you need to keep them.
Assumptions and limits
- Accuracy depends on your device and browser clock. It is fine for workouts, cooking, presentations and classroom use, but it is not certified timing equipment.
- The time is not saved. Reloading or closing the tab clears the stopwatch and the laps.
- If a computer goes to sleep while the stopwatch is running, some browsers do not count the sleeping time. Keep the device awake for long runs.
- Laps are copied as tab-separated text (Lap, Split, Total) so they paste cleanly into a spreadsheet. The CSV file also includes the raw milliseconds.
- After one hour the display adds an hours digit, for example 1:02:03.456.
Frequently asked questions
How accurate is this online stopwatch?
It measures to the millisecond using the browser high resolution clock, so the limit is usually your browser. Expect errors of a few milliseconds from the moment you press the button, which is far smaller than human reaction time.
Does the stopwatch keep running if I switch tabs or lock my phone screen?
The measurement does, because it stores the start time rather than counting ticks. The display catches up the moment you return. On a phone that actually suspends the browser, behavior depends on the operating system, so keep long timings in the foreground.
What is the difference between a split time and a total time?
A split is how long one lap took. The total is the running time from the very start. Splits add up to the final total, so 12.340, 12.760 and 11.920 seconds add up to 37.020 seconds.
Why does a screen reader not read the time as it changes?
Announcing a value that changes every few milliseconds would drown out everything else. The stopwatch announces only your actions, such as stopping or recording a lap, and you can read the display whenever you choose.
Can I save my laps for later?
Yes, but not inside the page. Use Copy laps to paste them into a note or spreadsheet, or Download CSV for a file. The tool itself never stores them. For fixed countdowns, try the online timer.