Reaction Time Test
Wait for the box to turn green, then click as fast as you can.
Overview
The Reaction Time Test measures how quickly you can respond to a visual cue. A red box waits for a random delay, then turns green; click it as fast as you can. The test reports your reaction time in milliseconds across multiple trials and computes your average, helping you measure mental focus, fatigue, or recovery from caffeine.
Most healthy adults score between 200 and 300 milliseconds. Below 180 ms suggests practiced reflexes or anticipation of the cue; above 350 ms indicates fatigue, distraction, or a slower display chain. The test is useful as a quick check-in before high-focus activities like driving, competitive gaming, or surgery prep.
How it works
The test waits a random uniform delay (typically 1 to 4 seconds) before changing the box's colour. This random window prevents you from anticipating the cue — if the delay were fixed, you'd start timing the cue instead of reacting to it, which the test catches as "too early" and flags as a false start.
When the colour change happens, the engine records the timestamp; when you click, it records the click timestamp and reports the difference. Most of the measured time is signal propagation: roughly 100 ms for the photons to register on your retina and travel to visual cortex, 100 ms for motor planning and execution, and the rest for display latency, USB polling, and browser event handling.
Examples
- Reaction time 180 ms is fast — competitive esports players commonly land here.
- 250 ms is a typical adult average.
- 320 ms is on the slow end of normal; consider whether you're tired or distracted.
- A "false start" indicates you clicked before the green appeared — usually because you started pre-clicking.
FAQ
Why does my reaction time vary so much between trials?
Reaction times are noisy. Take 5-10 trials and look at the median rather than any single result.
Does my hardware affect the result?
Yes. A high-refresh-rate monitor and a low-latency mouse can shave 20-40 ms compared with a 60 Hz display and a wireless mouse.
Is reaction time the same as reflex?
No. Reflexes are spinal (sub-50 ms); reaction time involves cortical processing and is much slower.
Can I improve my reaction time?
Practice, sleep, hydration, and avoiding alcohol or sedatives all help. The biological floor is around 150 ms for most adults.
Why does the test penalise early clicks?
Pre-clicking would mask anticipation as fast reaction. The early-click flag keeps the score honest.