The visible table puts the newest completed lap first for quick scanning. A data file should preserve chronological order, so LapWatch exports lap one first and the final lap last. Fixed English column identifiers make the small file predictable across interface languages.
Three fixed columns
The header is lap, split, total. Lap is a base-10 integer. Split and total are quoted ASCII HH:MM:SS.mmm values exactly like the interface. A UTF-8 byte-order mark helps common spreadsheet software open the file. No label, date, page URL, session identifier or hidden timestamp is added.
Check the file before reloading
Download is enabled after the first completed lap. Open the CSV and compare the first, one middle and final row with the visible table. Confirm every total is non-decreasing and each split equals the difference between adjacent totals. Reload only after the file is accepted, because the capsule deliberately has no saved history.
Know what the browser cannot promise
LapWatch is an informal in-page instrument, not an independent clock service. Closing or reloading the page clears every timestamp and lap. Device sleep, browser suspension and operating-system differences can affect what one browser reports. Keep another suitable method whenever the duration matters, and never use this tool for medical, emergency, food-safety, transport, industrial, official, legal or other safety-critical timing. The fixed 99:59:59.999 and 500-lap limits prevent a forgotten tab from pretending to provide unlimited continuity.