Reaction Time Test
Test your reaction speed. Click or tap as fast as you can when the screen turns green.
Disclaimer: The results provided by this tool are estimates for informational purposes only. Actual values may vary. Please verify important calculations independently.
How the reaction time is measured
The reaction time test records the number of milliseconds between a visual stimulus and your click. When you press Start, the browser schedules a random delay between roughly one and five seconds using a high-resolution timer, then recolours the screen from red to green. The moment the green frame is painted, a timestamp is captured from the same high-resolution clock. When you click, a second timestamp is taken and the difference is your reaction time. Using the browser's performance timer instead of the standard Date API avoids rounding to the nearest millisecond and keeps noise low.
A small amount of inherent delay is unavoidable. The display itself takes a few milliseconds to refresh — around 8 ms on a 120 Hz monitor and 16 ms on a 60 Hz monitor — and mouse, trackpad, and keyboard controllers add another 1 to 10 ms each. These delays are part of what is measured, so the same test on different hardware will produce slightly different raw numbers. The result is best compared against your own past attempts on the same setup, or used to rank several people in a room, rather than treated as an absolute biological figure.
When reaction time actually matters
A reaction time test is a quick way to check alertness, compare focus across different times of day, or gamify a coffee-break moment with friends. Drivers sometimes use it to see how much sleep deprivation or a glass of wine has slowed them down, since an extra 100 ms at 60 km/h equates to about 1.7 extra metres of stopping distance. Competitive gamers and esports players track reaction time as a baseline metric, and sports coaches occasionally use similar tools to screen for fatigue during preseason training. The average adult sits around 250 ms, under 200 ms is fast, and 150 to 180 ms is typical for trained professionals.
Several factors besides biology influence the score. A fresh attempt after you have calibrated to the button position will usually be faster than your first try, and attempts in a darkened room with a bright display tend to beat attempts in glare. Alcohol, heavy meals, illness, and sleep debt slow reactions measurably, while caffeine shaves a modest amount off. Reaction time also drifts upward with age, typically by a few milliseconds per decade after the mid-twenties. Treat the test as a lightweight check rather than a clinical measurement, and run multiple trials to average out the noise.