Reaction Time Test

Reaction Time Test measures how long it takes you to respond to something you see. Click to arm it, wait for the box to turn green, and click again as fast as you can. The time between the colour changing and your click is your reaction time, in milliseconds.

The delay before green is random between one and five seconds, which is the whole design of the test. A fixed delay would be learnable within three attempts, and the test would then measure rhythm rather than reaction. Clicking before the green is caught and called out rather than quietly restarting, because jumping the gun is the most informative thing that happens on this page — it shows the moment where anticipation replaced reaction.

Around 250 milliseconds is typical for an adult reacting to something seen. That figure includes the light reaching your eye, the signal travelling to your brain, the decision, the signal travelling back to your hand and the switch in the mouse closing — so part of what is being measured is your equipment, not you. A wired mouse on a fast screen will read a few tens of milliseconds quicker than a wireless one on a slow television, and neither number says anything about the person. Compare your own attempts against each other rather than against somebody else's.

• A random one to five second delay, so the cue cannot be predicted
• Early clicks caught and explained rather than silently ignored
• Best, average and attempt count kept across the session
• A verdict against the typical 250 millisecond figure
• Keyboard support: space or enter instead of clicking
• Results copied as text in one press
• Nothing stored and nothing uploaded
• Colour changes paired with text, so the state is not colour alone

The reaction time test is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

• Checking how alert you are at different times of day
• Comparing reaction times with somebody else on the same computer
• Seeing the effect of tiredness on reaction speed
• Testing whether a new mouse or screen feels faster
• Demonstrating reaction time in a lesson