Stopwatch

It keeps correct time in a background tab

The most useful thing here, and the thing most browser stopwatches get wrong.

Browsers deliberately slow down inactive tabs to save battery. A stopwatch that counts its own ticks — adding ten milliseconds every ten milliseconds — loses time whenever it is throttled. Switch away for five minutes, come back, and it is short. People discover this after the thing they were timing has finished.

This one does not count. It records when you started and works out the elapsed time by subtraction, from a clock that cannot run backwards or be affected by the system time changing. If the tab is throttled, the display stops refreshing — but the moment you look at it again, the number is exactly right, because it was never being accumulated in the first place.

The practical upshot: you can switch tabs, minimise the window or lock the screen and the total will still be correct. Pause and resume are handled the same way, so they do not introduce drift either.

One thing that is genuinely affected: if the tab is throttled at the moment you hit Lap, the lap is still recorded accurately, but you may not see the display update until you return. The recorded times are right regardless.

Lap and split are different things, and you get both

Worth understanding, because most web stopwatches show one and label it the other.

Lap is the time for that segment alone — from the previous lap to this one.

Split is the total elapsed time at the moment you pressed it.

Time four laps of a track at roughly ninety seconds each and your fourth lap is about 1:30 while your fourth split is about 6:00. Both are useful and they answer different questions: the lap tells you how that effort went, the split tells you whether you are on pace overall.

The table shows both columns for every lap, plus a third: the difference against the previous lap, signed, so a slower lap shows a plus and a faster one a minus. That column is the one you actually read while working — it tells you immediately whether you are speeding up or fading, without any arithmetic.

Your fastest and slowest laps are highlighted, and a summary line gives the lap count, the fastest time and the average. Newest laps appear at the top, so the one you just recorded is where you are already looking.

Use the keyboard

Faster and more accurate than clicking, which matters when you are timing something and watching it rather than the screen.

Space starts and stops. L records a lap. R resets.

Two thoughtful details. R only works when the stopwatch is stopped, so you cannot wipe a running session by mistake — which is the single worst thing a stopwatch can do to you. And the shortcuts are ignored while you are typing in a field, so they will not fire unexpectedly.

For repeated timing — sets, intervals, laps on a track, stages of a process — keeping a finger on L is considerably more reliable than aiming at a button, and it avoids the small delay of moving the mouse.

Export the laps before you close the tab

The honest limitation, and it has a straightforward answer.

Nothing is saved. There is no storage of any kind, so refreshing the page, closing the tab or navigating away loses every lap you have recorded. There is no recovery.

That is a deliberate consequence of the tool storing nothing about you, but it means one habit is essential: export before you leave.

Download CSV gives you a file with the lap number, lap time, split time and difference in columns — ready to open in Excel, Sheets or Numbers, where you can chart it or compare sessions. This is the one to use for anything you will look at later: training sessions, process timings, repeated measurements.

Copy as Text puts the same information on your clipboard as readable lines, for pasting into a message, a notebook, a log or a training diary.

If you are timing something long, export partway through rather than waiting for the end. It costs a click and removes the risk.

What it is good for

Interval training and track work, where the lap-versus-split distinction and the difference column are exactly the numbers a runner or swimmer wants, and the CSV export means a session can go straight into a training log.

Timing a process at work — how long a build takes, how long each stage of a task runs, how long customers wait. The stats line and the export turn a stopwatch into a measurement, and measuring three times and taking the average is where the average matters.

Cooking, presentations, exams and practice, where you want elapsed time rather than a countdown.

Anything where you need the numbers afterwards, which is the real dividing line: if the result matters once and then does not, a phone stopwatch is fine. If you want the lap table, the comparison and a file, that is what this is for.

If you need to count down to something rather than up, Countdown Timer is the other tool — and its page explains the tab-throttling problem from the other side.

Everything runs in your browser and nothing is transmitted or stored. Once the page has loaded it works offline, so a dropped connection mid-session changes nothing.

Related tools

Countdown Timer counts down to zero instead of up, for anything with a deadline. Unit Converter handles the conversions that come up alongside timing, such as pace and speed. Random Number Generator is the one for drawing a starting order rather than timing it.