Online Stopwatch

Most free stopwatches have one infuriating habit. Refresh the page, bump the tab, or let the browser reload it, and your time is gone. This one keeps going through all of that. Leave it running, close the window, reopen the page an hour later, and the count is still climbing from where it should be, laps and all. That alone is the reason to pick it over the ad-choked stopwatch you probably found first.

It counts up from zero so you can measure exactly how long something takes. A lap on the track, a study block, a recipe step, a reaction in a lab. Press Start and the big display climbs in hours, minutes, seconds, and hundredths. Stop pauses without losing your place, Start picks it back up, Lap marks a split without breaking the count, and Reset clears everything to zero. You can drive all of it from the keyboard too, so your hands never leave the race. It runs in your browser. Nothing to install, no account, no numbers buried under a banner.

1. Press Start to begin. The display counts up in HH:MM:SS.cs, which is hours, minutes, seconds, and hundredths of a second.
2. Press Lap to mark a split. Each one lands in the list below the buttons with its own split time and the running total at that moment, newest on top.
3. Press Stop to pause with the current time still on screen. Press Start again to carry on from that exact point. Paused time never counts toward your total.
4. Press Reset to send the display back to zero and clear the laps. It works whether the clock is running or already paused.
5. Use Copy laps to drop the whole list (lap number, split, and total) onto your clipboard as plain text, ready for a note or a spreadsheet.

Space toggles Start and Stop. L records a lap, but only while the clock is running, so you can't log a split against a stopped watch. R resets, but only when the stopwatch is stopped, which keeps you from wiping a live run with one stray key.

Those guards matter, because trackside or mid-experiment you're watching the action, not the display, and a shortcut that fires the wrong thing is worse than none. The browser still owns anything with Ctrl or Cmd held down, so Ctrl+R reloads and Cmd+L jumps to the address bar. The plain single keys belong to the stopwatch, and even a stray reload won't cost you your time.

The stopwatch quietly saves its state in your own browser as you go, which is the one thing the throwaway stopwatches never bother to do. So if the page reloads, the tab crashes, or you close everything and come back later, it reads that saved state and drops you right back where you were, with a small note under the display to say so.

If the clock was running when you left, it stays running and counts the real time that passed while you were gone, which is deliberate. A stopwatch measures how long since you hit Start, so an hour away is an hour on the clock, like a real one left ticking on a bench. To freeze it, press Stop, and a paused session comes back paused at the same number.

A few honest limits. The saved session lives in the browser you were using, so another browser or device won't see it, and clearing your browsing data clears it. Private or incognito windows usually forget everything the moment you close them, so treat those as single-sitting. When it matters, Copy laps first and you'll have the splits either way.

Every lap shows two numbers, and mixing them up is the most common mistake with a lap timer. The total is the time from your first Start to the moment you pressed Lap. The split is narrower. It's just that one lap, the gap between this mark and the one before it.

A quick example. You hit Lap at 1:30, again at 3:10, and once more at 4:25. The totals are 1:30, 3:10, and 4:25, always climbing. The splits are 1:30, 1:40, and 1:15, because each split is only the slice since the last mark. They add back up to the final total, a tidy check if a reading ever looks off.

Why care? Totals only ever go up, so they can't tell you that lap three beat lap two. The split column is where that shows up. It catches the lap where you finally sped up, or the exact moment you started to fade, none of which shows if you only watch the total. Compare the splits when you want to see how your efforts stack up against each other, and read the total when you just want your time so far.

Intervals on the track or in the pool. Start at the whistle, tap Lap at the end of each rep, and the split column shows how each effort stacked up. Coaches catch where an athlete fades, and the whole set copies straight into a training log.

Lab work and long experiments. Reaction times, observation windows, how long a solution takes to change color. The lap list is a clean record of every trial, and a long observation is exactly when a stray reload might sneak in, so the saved session means a refresh doesn't wipe an afternoon of readings.

The stopwatch works out elapsed time from your device's real clock, not by counting screen redraws, which is why it holds accurate over long runs and while the tab sits in the background. It shows hundredths, but your own reaction time on the buttons swamps any sub-millisecond difference, so for close calls the trend across many laps tells you more than one reading.

It also helps to know when you want something else. A stopwatch counts up and runs until you stop it, for measuring something whose length you don't know yet. A countdown timer is the opposite, you set a length and it counts down to zero, which suits a known bake time or a capped meeting. Use this when you want to know how long something took. Reach for a timer when you need to be told that a set amount of time is up.