ITStopwatch
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Tool guide
A stopwatch is what you need when the duration is unknown in advance: how long a set at the gym really takes, a test run, a client call, a project build. It counts up from zero with milliseconds, the Lap button drops a marker without stopping the clock, and the Laps panel shows both the total at each marker and the gap from the previous one. It all runs in the tab, so your measurements stay with you. See also: count down from a set number of minutes, pomodoro timer for work sessions, count the days between two dates.
A stopwatch counts up from zero and runs until you stop it — it answers the question 'how long did that take'. A timer counts a set interval down and alerts at zero, answering 'how much is left'. Timing a set of squats calls for a stopwatch; boiling an egg calls for a timer.
The display refreshes on animation frames while the elapsed time itself comes from the system clock, so over seconds and minutes the error is negligible. Visible drift only happens in a backgrounded mobile tab, where the browser throttles rendering; the number catches up as soon as you return to it.
Both. Each lap row carries the time since Start and the interval since the previous marker. The first lap matches the total, after that they diverge — and it is the interval column you compare when reviewing sets at the gym or stages of a build.
There is no export button. Laps live in the open tab, and Reset or a page reload clears them. If you need the numbers later, select the list and copy it into notes or a spreadsheet before resetting. Nothing from the measurement is sent anywhere, so the only copy is yours.
The page opens and runs on a phone, but locking the screen puts mobile tabs to sleep. Elapsed time recovers when you unlock, yet you cannot tap Lap while it is asleep. For long measurements with a dark screen, the phone's built-in stopwatch is the safer choice.
There is no hard cap; the list simply grows and scrolls. After a few hundred markers it becomes awkward to read rather than slow to compute. For long sessions, split them up: copy the figures, press Reset, and start the next block with a clean list.
Before: Five sets in a row, each timed separately
After: Total 00:04:12.480; laps 48.120 / 50.640 / 47.900 / 52.310 / 53.510, best is the third
Before: Not clear which stage of the pipeline is slow
After: One lap per stage: 12.4 s install, 6.9 s lint, 71.2 s tests
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