Timers
Stopwatch
Free online stopwatch with lap and split times, accurate to the hundredth of a second, that keeps counting correctly if you switch tabs or lock your screen.
Stopwatch
Space to start/stop · L to lap
Lap and split times
Split is the time for that lap alone; cumulative is the total elapsed time when it was recorded — they are different numbers. Fastest and slowest lap highlighting turns on once at least two laps have different splits, and there is no limit on how many laps you can record.
No laps yet. Press Lap (or the L key) while the stopwatch is running to record one.
Online stopwatch with laps
This is a straightforward online stopwatch: press Start, and the display counts up from zero in minutes, seconds and hundredths of a second. Press Lap at any point while it's running to record a split without stopping the clock, press Stop to pause it, and Resume to pick up exactly where you left off. Nothing you do here is sent anywhere — the entire stopwatch runs in your browser, and nothing is saved once you leave or reload the page.
Hundredths of a second are shown at all times, not just seconds, because that's the resolution most people actually want out of a stopwatch — timing a task down to the second is rarely precise enough once you're comparing two runs that finished within a second of each other.
Reading your laps: split vs. cumulative time
Once you've recorded at least one lap, the table below the clock shows two numbers per lap, and they answer two different questions. Split is how long that particular lap took on its own — the time since the previous lap, or since you pressed Start for the very first one. Cumulative is the total time on the main clock at the moment you recorded that lap. If you're pacing yourself against a target per-lap time, read the split column; if you want to know how far into the whole session you are, read cumulative. Once you have at least two laps with different splits, the fastest one is marked and the slowest one is marked, so you don't have to scan the column and compare it in your head.
Switching tabs vs. closing the tab: what actually survives
A background browser tab has its timers throttled by the browser to save battery, and a locked phone can suspend a page's JavaScript entirely — both are normal, and both are exactly the situation this stopwatch is built to survive. It does that by recording the real clock time you pressed Start and reading the real clock time again whenever it needs a number, rather than by counting how many times a timer fired while you were away. So switching tabs, minimising the browser, or locking your screen and coming back five minutes later shows five minutes elapsed, not a number that's fallen behind. Closing the tab is different: it ends the page entirely, so there's nothing left running to come back to, and a reload always starts fresh at zero.
Long sessions: past an hour, and past a day
The display adds an hours field automatically once you pass sixty minutes
(01:00:00.00 instead of wrapping the minutes back to zero), so a long session
never becomes ambiguous. If you genuinely leave a tab running for more than a day,
the hours field just keeps growing past 24 rather than switching to a days counter
— unusual, but the layout keeps its shape rather than breaking.
Questions
- Does an online stopwatch keep running if I close the tab?
- No. Closing the tab, or reloading the page, ends the session completely — nothing about this stopwatch is saved between visits, so a fresh load always starts back at zero. That's a different thing from switching to another tab or app without closing this one: as long as the tab itself stays open somewhere, the clock keeps counting correctly in the background, because it's reading the actual time of day rather than counting ticks. Closing the tab removes the page that's doing that reading, so there's nothing left running.
- What's the difference between a lap's split time and its cumulative time?
- Cumulative time is the reading on the main stopwatch at the moment you pressed Lap — the total elapsed time since you hit Start, including every earlier lap. Split time is only the gap since your previous lap (or since Start, for lap one) — how long that one stretch took on its own. They're the same number for your first lap and different for every one after that, which is exactly why both columns are shown side by side rather than just one: if you only see cumulative time, you have to do the subtraction yourself to know how a single lap actually went; if you only see split time, you lose track of how far into the whole run you are.
- Why did my stopwatch jump ahead after I unlocked my phone or switched back to this tab?
- That's correct behaviour, not a bug. This stopwatch never counts by adding up small ticks — it records the exact moment you pressed Start (or Resume) and, every time it needs to show a number, subtracts that from the current time. A backgrounded tab or a locked screen doesn't stop the clock on your device, so when you come back the subtraction still gives the true amount of time that passed, even though the page itself was doing nothing on screen the whole time. A stopwatch that instead counted ticks would under-report exactly this situation, since a hidden tab's timers are throttled or paused by the browser — which is the opposite, and wrong, direction to fail in.
- Is there a limit to how many laps I can record?
- No. Every lap you record while the stopwatch is running gets added to the list, and the list scrolls once it gets tall rather than cutting off — there's no maximum built into it. The newest lap appears at the top of the table so you don't have to scroll to see your latest split.
- Can I use the keyboard instead of clicking the buttons?
- Yes. Space starts the stopwatch, and pressing it again while running stops it (pressing it once more resumes); L records a lap while the stopwatch is running. Both shortcuts are ignored while you have one of the page's own buttons focused, so tabbing to Reset and pressing Space activates Reset rather than restarting the clock.