Each lap is an immutable checkpoint. Its split measures the interval since the previous lap; its total measures the session so far.
Two useful ways to read a lap
Start begins a stopwatch at zero. Lap records the elapsed session total at that moment. The split subtracts the previous lap’s total, so it measures just the interval between those checkpoints. The first split equals the first total. Newest laps appear first in the page, while copied output uses chronological order with Lap, Split and Total headings.
| Lap | Split | Total |
|---|---|---|
| 1 | 00:12.0 | 00:12.0 |
| 2 | 00:08.5 | 00:20.5 |
| 3 | 00:10.0 | 00:30.5 |
Pause without changing the history
Pause stops accumulating time; Resume adds only time spent running. Existing lap snapshots do not change when the live display advances. A late callback recomputes elapsed time from the clock reference, and changing the device’s wall clock during active use does not reset the stopwatch.
The local tool holds up to 1,000 laps and up to seven days of elapsed time. The page explains those bounds rather than silently discarding older laps. Reset asks before clearing progress and lap history. A clipboard failure offers selectable text, so the result can still be copied manually.
Recovery belongs to this tab
The stopwatch uses session storage for reload and history return in the same tab. Closing the tab normally ends that storage session; browser session-restore behavior can vary. A new independent tab does not serve as a synchronized copy of this stopwatch. Save copied lap text elsewhere when you want a durable record.
Running recovery includes time away using paired trusted UTC when available, otherwise a device-clock estimate with an uncertainty notice. Paused recovery excludes time away. Completed lap totals stay unchanged even if a recovered running total is refined. Storage failure leaves a usable in-page session and tells you recovery is unavailable.
Keep the result readable
The presentation view removes surrounding page distractions while retaining access to the controls. Exit returns to the control that opened it. Keyboard shortcuts are ignored while you type in an input, so copying or editing text should not pause or reset a session.
Displayed tenths make elapsed time easy to scan, but do not establish certified timing precision. Browser scheduling, device suspension and uncertain recovery affect what an ordinary web tool can promise. Use independently suitable equipment when the measurement needs a formal guarantee.