ONE SIGNAL · ONE RESPONSE
Wait for the signal. Respond the instant it appears.
Record five valid reactions. False starts count as incorrect and must be retried.
READY?
Start a run, stay still through the random delay, then respond.
Respond with Space, Enter, a mouse click, or a tap. Responding before the signal is a false start.
HOW TO PLAY
Start the test and wait through a random delay of 1 to 3.2 seconds.
When the large green signal appears, press Space or Enter, click, or tap immediately.
Complete five valid reactions for your average. An early response is recorded as incorrect and does not replace a valid trial.
ABOUT THE TEST
Simple reaction time is the delay between detecting one expected signal and making one known response. There is no choice between targets: your only job is to respond as soon as the signal appears.
This browser test measures from the visual signal to your input. Screen refresh rate, browser scheduling, keyboard, mouse, touchscreen, and device latency can all affect the result.
ENDLESS CHALLENGE
Endless mode gives you less time to respond after each correct signal. Your score is the number of consecutive correct reactions.
The first false start or timeout ends the run, so patience before the signal matters just as much as speed after it.
QUESTIONS
Results vary with age, attention, practice, and hardware. Roughly 200–300 ms is common in browser-based visual tests, but your most useful comparison is repeated testing on the same device.
A randomized delay makes it harder to respond by rhythm or prediction. The signal can appear at any point between 1 and 3.2 seconds after a trial begins.
Any Space, Enter, click, or tap before the signal appears is a false start. It counts as an incorrect response but does not count toward the five valid reactions in Standard mode.
Yes. Tap the large reaction area when it turns green. Touch and keyboard latency differ, so compare results collected with the same input method and device.
No. This game is for recreation and personal comparison. It is not a clinical assessment and cannot diagnose a health condition.