User Guide
Press Start
Timing begins immediately. There is nothing to set up first — no account, no options, no permission prompt — which is the point of a stopwatch. The same button pauses and resumes once it is running.
Record laps as you go
The Lap button stays disabled until the clock is running, then records the moment you press it without interrupting the count. Each lap is added to a table beneath, so you can see how one interval compares with the last rather than trying to remember it.
Read the table
Laps stack in order as you record them. That list is the useful part — a single elapsed figure tells you how long something took, whereas a column of laps shows whether you were speeding up, slowing down, or holding steady.
Reset when you are done
Reset returns the clock to zero and clears the recorded laps. Copy anything you want to keep before pressing it, since the list is not saved anywhere.
About the Online Stopwatch
Opens in a tab, starts on one click, records laps. No install, no account, no permission prompt — which is the entire requirement when you need to time something in the next four seconds.
Which clock it reads, and why that choice matters
Timing does not use the wall clock. It uses the browser’s high-resolution monotonic timer, performance.now(), which counts steadily forward from when the page loaded and is unaffected by anything that changes the system clock. That distinction is not academic: if your computer syncs its time mid-session, or daylight saving shifts, a stopwatch reading the wall clock can jump or even run backwards. A monotonic clock cannot.
How laps are stored
Each lap records the elapsed time at the moment you pressed, not a duration. Intervals are derived by subtracting consecutive readings. Storing absolute readings this way means no rounding error accumulates across a long session — the twentieth lap is as accurate as the first, which would not be true if each interval were measured separately and added up.
Why the lap table is the useful part
Any device can tell you something took eleven minutes. What is harder, and far more informative, is that the first third took three minutes and the last third took six. That shape is what tells a runner they went out too fast, a presenter that their middle section overruns, or a team that a process degrades as it repeats. Recording those by hand while also doing the task is how errors enter; a button that logs without stopping the clock removes the problem.
Accuracy, honestly stated
The timer resolves far finer than you can react. Human reaction time to a visual cue sits around a fifth of a second, which is orders of magnitude larger than any error in the clock. For anything where hundredths decide an outcome, hand timing is the wrong instrument regardless of what runs it.
One thing to know
Nothing is stored. Reloading or closing the page clears the clock and the laps, so copy anything you need before you reset. Browsers also throttle timers in background tabs, so switching away can make the display catch up in a jump when you return.
Frequently Asked Questions
Why is the Lap button greyed out?
It only becomes active once the stopwatch is running. There is nothing to record before that, so it stays disabled to make the state obvious.
Are my lap times saved?
No. Reloading or closing the page clears everything. Copy the times you need before you reset or leave.
Does it keep timing if I switch tabs?
The clock continues, though browsers throttle background tabs, so the display may catch up in a jump when you return rather than updating smoothly throughout.
How accurate is it really?
Well within human reaction time, which is the actual limiting factor at perhaps a fifth of a second. For officiating anything where hundredths matter, hand timing of any sort is the wrong method.
Can I use it offline?
Once the page has loaded, yes. Timing is done by your browser with no further requests.
What is the difference between this and the Countdown Timer?
A stopwatch counts up from zero to measure something as it happens. The Countdown Timer counts down to a fixed date and time you set in advance.