REACTION TIME TEST / GUIDE

How Reaction Time Testing Works

A browser reaction time test presents an unpredictable visual signal and measures the interval until a response event reaches the page.

Why the cue is randomized

A fixed countdown encourages anticipation. This app uses a randomized 1.5–4.5 second wait, then applies the visible NOW state inside a browser animation-frame callback.

High-resolution browser timing

The app records cue and response baselines with the browser performance clock. That clock is monotonic, so system clock adjustments do not move it backward. Individual results are displayed as rounded whole milliseconds while calculations preserve finite raw values.

What the milliseconds include

The number is browser-observed, not a laboratory measurement of biology alone. Display presentation, browser scheduling, the operating system, device firmware, and input-event delivery can all contribute to the measured interval.

Why use the median?

With five valid rounds, the median is the middle reaction time after sorting. It is less affected than the mean by one unusually slow attempt. The average is still shown as useful context.

Worked session

For 200, 220, 240, 260, and 280 ms, the median is 240 ms, the average is 240 ms, the best is 200 ms, and the slowest is 280 ms.

False starts

An accepted input during WAIT is recorded only as a false start. It cancels the pending cue, records no reaction time, and leaves the same numbered round to be retried.

Compare like with like

Mouse, pen, touch, and keyboard paths are different. The first valid response locks the session so one result summary never mixes those input classes. Repeated comparisons are most meaningful on the same browser, display, device, and input method.

What this test is not

This is not a medical reflex examination, neurological assessment, driving-fitness test, monitor response-time measurement, server response-time test, or anti-cheat system.