How the reaction time test works
Click the box to begin. It turns red and you wait. After a random delay of between 1.5 and 4.5 seconds it turns green, and you click, tap or press Space as fast as you can. The time between the box turning green and your response is your reaction time, measured in milliseconds, or thousandths of a second. After five rounds you get your average, your fastest and slowest rounds and a rating.
Clicking while the box is still red is a false start. That round is not scored and you simply try it again. Because the delay changes every time, guessing does not help: the only way to score well is to watch closely and react.
What is a normal reaction time?
In laboratory conditions, young adults take roughly 190 milliseconds on average to respond to a simple visual signal and about 160 milliseconds to respond to a sound. On a computer test like this one the numbers are usually higher, often between 200 and 300 milliseconds, because the screen, mouse, operating system and browser each add a small delay. A screen that refreshes 60 times per second, for example, only draws a new picture every 16.7 milliseconds.
That is why your result is best compared with your own earlier scores on the same device. A gap of 10 to 20 milliseconds between two computers often says more about the hardware than about you.
What affects your reaction time?
- Attention: brief lapses in concentration cause the slow rounds that pull your average up, which is why the test uses five rounds instead of one.
- Tiredness: a lack of sleep slows responses noticeably, so you may score better when you are fresh.
- Age: reaction speed improves through childhood, peaks in early adulthood and slowly declines from middle age.
- Practice: repeating the test helps a little, mostly because you become calmer and more focused. Trying to guess the moment the light changes mainly leads to false starts.
- Equipment: a wired mouse, a high-refresh-rate monitor and closing other heavy programs can each shave off a few milliseconds.
Why reaction time matters
Quick reactions count in sports, in fast games and on the road. A car travelling at 100 km/h covers almost 28 metres every second, so even a quarter of a second of reaction time means several metres before the driver's foot reaches the brake. This test is a fun way to check how alert you feel today. It is not a medical or driving assessment.
Frequently asked questions
How is my reaction time measured?
With your browser's high-resolution timer, from the frame in which the box turns green to the moment your click, tap or key press arrives.
Why is my score different on another device?
Screens, mice, touch screens and browsers each add their own small delay. Compare results on the same device for a fair picture.
What counts as a false start?
Any click or key press while the box is still red. The round is not scored, and you repeat it.
Can I use the keyboard instead of the mouse?
Yes. Press Space or Enter instead of clicking. Many people find a key slightly faster than a mouse button.
Is 200 milliseconds a good result?
Yes. On a computer test, where the equipment adds its own delay, an average around 200 ms is very fast.
Does the test work on phones?
Yes. Tap the box when it turns green. Touch screens can add a little delay, so phone results are often slightly slower than with a mouse.
