Click the pad to start. It turns red and waits a random amount of time, then flips to green. The moment it turns green, click as fast as you can — the gap between green appearing and your click is your reaction time in milliseconds. You do this five times and get an average.
Why a random wait?
The delay before green is randomised (roughly 1.2 to 4 seconds) so you can't predict it and time your click in advance. You have to actually react to the colour change.
What happens if I click too soon?
If you click while it's still red, that attempt is voided and you'll see a "Too soon!" screen. Click again to retry that same attempt — early clicks never count as a fast score.
Timing & scores
How accurate is the timer?
Timing uses the browser's high-resolution clock (performance.now()), so the measurement itself is sub-millisecond. In practice your monitor's refresh rate and input lag add a little overhead, so treat the number as a very good estimate rather than a lab-grade figure.
What's a good reaction time?
For a simple visual click test, most people land around 200–270 ms. Under 200 ms is fast, and around 150 ms is near the human limit for this kind of task. Tiredness, screen lag and input device all affect the result.
Privacy
Is anything saved or uploaded?
No. Everything runs in your browser. No times or data are sent anywhere, and reloading the page clears your results.
