Reaction time test

How to use it

1. Click the box (or press Space). It turns red.
2. Wait. After a random 1.5 to 4.5 seconds it turns green.
3. Press as fast as you can. Your time in milliseconds is shown.
4. Click again for another try. Best, mean and median update after every try.

How it works

The clock starts when the colour changes and stops on the press event, both read with performance.now(). The median of an even number of tries is the average of the two middle times.

Worked example

Tries of 180, 240 and 300 ms give a best of 180 ms, a mean of 240 ms and a median of 240 ms.

Tips

• Use the same device and sit the same way when you compare days.
• Ignore the first try; most people are faster once warmed up.
• Pressing early only resets the try, nothing is lost.