How it works

1. Tap the panel to begin. It turns red.
2. Wait. After a random delay of one to five seconds it turns green.
3. Tap the instant you see green. The time between the colour change and your tap is your reaction time.
4. Tapping while it is still red counts as a false start and that round is repeated.
5. After five rounds you get your average.

Your best average is kept in this browser so you can try to beat it later. Nothing is stored anywhere else.

What counts as fast

Simple visual reaction time for adults usually lands around a quarter of a second. Part of that is biology — light hitting the retina, the signal reaching the brain, the command travelling back down to your finger — and no amount of practice removes it.

Things that change your score

Touchscreens add latency of their own, so a phone result is typically slower than a mouse click on a wired desktop display. Tiredness, caffeine, screen refresh rate and how much you are anticipating the change all move the number. For a fair comparison, test yourself on the same device twice rather than comparing against someone else's phone.

This test is for entertainment and curiosity only. It is not a medical or diagnostic tool and says nothing about your health.