| # | Split | Total | vs avg |
|---|
Every mode computes elapsed time as now − startTime from one fixed reference, so a slow tick costs nothing and drift cannot build up.
An alarm app may run with the screen off; a browser tab never will. The alarm screen says so rather than letting you find out.
The statistics, the export, the interval work, and any device with a browser: mean, median, standard deviation and a consistency score.
Early presses reset the test, because fast times only mean something if the stimulus came first. Includes your keyboard, mouse and display lag.
Adding up tick intervals compounds every small delay into permanent drift. Computing now − startTime fresh each frame means a single slow tick costs nothing: the next frame is still measured against the same fixed origin. Scheduling audio needs the same idea taken further, against the audio hardware’s own clock, which is what the Metronome does.
Two runners can average the same lap time while one holds dead-steady splits and the other swings wildly. The consistency score (100% minus the coefficient of variation of your splits) exists because the average alone cannot tell them apart.
Screen refresh rate, input polling and click latency all sit between the colour changing and your click being recorded: a faster monitor or mouse can shave real milliseconds with no change in neurology.
Stopwatch with laps: yes, plus mean, median, standard deviation, a consistency score, a pace chart and a CSV; a stock app gives best and worst. Timers, several at once, named: yes, with add-a-minute, pause, repeat and restart. World clock: yes, with a 24-hour strip per city. Interval trainer: yes, with Tabata, HIIT and boxing rounds. Reaction timer: yes, with early-press rejection. Alarm at a wall-clock time: partly (below). Bedtime and sleep schedule: no: that is an alarm plus a health app, and the health half is not something a web page should pretend to.
A web page cannot wake you up. An alarm app is granted the right to run when the screen is off and the phone is locked; a browser tab is not, and never will be, because that permission is the security boundary between a web page and an installed application. A page can hold the screen awake while in front of you, raise a notification if you allow one, and be loud when it fires: a kitchen, a desk, a laptop next to you. It does not cover a flight at six in the morning, and the alarm screen says so.
Green means that lap was faster than your running average, red slower: a quick read on whether you are speeding up, slowing down or holding steady. Tabata is 20 s work and 10 s rest × 8, from Izumi Tabata’s 1996 study; the HIIT and boxing presets follow widely used conventions.
Green means that lap was faster than your running average, red means slower — a quick visual read on whether you're speeding up, slowing down, or holding a steady pace, without doing the maths yourself.
It's 100% minus the coefficient of variation across your laps — the standard deviation of your splits relative to their average. A high score means every lap took about the same time; a low score means your pace swung around a lot, even if the average looked fine.
Clicking before the colour changes means you were guessing the timing, not reacting to it — genuinely fast reaction times only mean something if the stimulus came first. Real reaction-time research discards early responses for the same reason.
Tabata (20s work/10s rest ×8) is the original protocol from Izumi Tabata's 1996 study on high-intensity intermittent exercise; the HIIT and boxing-round presets follow widely-used conventional training formats. Custom rounds let you build any protocol beyond these defaults.
That your device reports time honestly, and that a few milliseconds either way does not matter. Precision is bounded by browser event timing and screen refresh rate, so treat the last digit as indicative. Browsers deliberately throttle background tabs — elapsed time stays correct because it is measured against a fixed reference, but on-screen updates and alerts may lag until you return to the tab. Audio cues carry their own output latency, and reaction-time results include your keyboard, mouse and display lag as well as your own.
Releases in which this page changed, newest last. Derived from the archived copy of every release, not from notes written afterwards — so it reflects what actually shipped. Site-wide passes are left out; they are in the full changelog.