A stopwatch that doesn’t drift
A stopwatch sounds trivial, but a naive one is wrong by design. The obvious approach — add ten
milliseconds to a counter on every setInterval tick — slowly falls behind real
time, because the browser never fires those ticks on a perfect schedule. Layout work, garbage
collection and background throttling all delay them, and the error accumulates: a counter like
that can lose several seconds over an hour.
This tool avoids that entirely with delta timing. When you press Start it
records a single timestamp, and on every animation frame it shows
now − start — the genuine elapsed time. The interval between frames no longer
matters, so the clock stays exact whether the page is idle or busy, and it snaps to the right
value the instant you return from another tab.
Laps and splits, worked through
Say you’re timing four laps of a track. You start the clock and tap Lap as you cross the line each time. The split column shows the cumulative total at each tap — your running clock — while the lap column shows just the slice since the previous tap:
| Lap | Lap time | Split (total) |
|---|---|---|
| 1 | 01:02.40 | 01:02.40 |
| 2 | 00:58.10 | 02:00.50 |
| 3 | 01:05.30 | 03:05.80 |
| 4 | 00:57.90 (fastest) | 04:03.70 |
Lap 4 is your quickest split and lap 3 the slowest; the live tool flags both automatically so pacing trends jump out without any mental arithmetic.
Where millisecond timing earns its keep
Training & sport
Track running, swimming and cycling splits to see exactly where pace is gained or lost across a session.
Cooking & process timing
Time pour-over coffee, espresso shots, interval workouts or anything where a few seconds changes the result.
Quick benchmarks
Hand-time how long a task, demo or page interaction takes when wiring up a formal measurement isn’t worth it.