Stopwatch

// Why the time on screen is the real time

Most browser stopwatches are built by adding a fixed amount to a counter on a timer: ten milliseconds, a hundred times a second. That is fine until the tab loses focus, the laptop sleeps, or the machine is simply busy, at which point the browser throttles the timer and every skipped tick is time that silently never gets counted. Leave one of those running in a background tab for ten minutes and it can come back visibly short.

This one never accumulates. It records the timestamp when you press start and, on every frame it draws, subtracts that from the current time. Frames dropped while the tab was hidden change how often the number is repainted and nothing else, so the reading you come back to is correct whether the tab was in front the whole time or not.

The display truncates hundredths rather than rounding them. Rounding up would let the clock read one full second while only 0.999 seconds had actually passed, which is a stopwatch that fires early. Truncating means the number shown has definitely already happened.

// Laps, and what the table tells you

Press Lap and the current interval closes and a new one opens. The table shows each lap's own duration alongside the cumulative time at that point, because those answer different questions: the split tells you how that interval went, the total tells you where you are in the session.

Fastest and slowest are marked automatically across completed laps, which is the comparison you would otherwise make by squinting. The lap currently running is shown too, marked as in progress, but is deliberately excluded from that comparison, because a lap that has just started is shorter than every other lap until the instant it isn't, and letting it win would make the highlight flicker on every frame.

Copy laps puts the whole table on your clipboard as tab-separated text, which pastes into Excel, Numbers, or Google Sheets as proper columns rather than one mashed-together cell.

// Built for the hand that is already busy

Timing something usually means your attention is on the thing, not the screen. Space starts and stops, L takes a lap, R resets, so a whole session can run without ever finding the cursor.

There is no signup, no ad interrupting the count, and nothing to install. The page also keeps working with the network off once it has loaded, because the clock comes from your own device.

// fair questions

Does the stopwatch keep running if I switch tabs?

Yes, and it stays accurate. The elapsed time is measured from the timestamp when you pressed start, not counted up tick by tick, so a browser throttling the background tab changes how often the display repaints without affecting the time it shows.

What happens if I close or reload the page?

The stopwatch resets. Nothing is stored between visits: there is no account, no cookie holding your session, and no server that ever sees it.

How many laps can I record?

As many as you like; there is no cap. Copy laps exports the whole table as tab-separated text that pastes into a spreadsheet with the lap number, split, and total in their own columns.

Why does the fastest lap marker ignore the lap I am running?

Because a lap that started two seconds ago is shorter than every completed lap until it overtakes them, so including it would move the marker on every frame. The running lap still appears in the table, labeled as in progress; it joins the comparison once you close it.

Is it accurate to the millisecond?

The underlying measurement uses the browser's high-resolution clock, and the display shows hundredths of a second. Browsers deliberately reduce timer precision slightly as a privacy measure, so treat this as accurate to a few milliseconds. That is plenty for anything a person starts and stops by hand, and it is not a substitute for instrumentation in a lab.

Can I use it without a mouse?

Yes. Space starts and stops, L records a lap, and R resets. The buttons are also reachable by tab and work with a screen reader.