ReactionTest
Wait for green. Click the instant it flips.
5 rounds. After the countdown, the screen turns red. The moment it flips green, click anywhere. Click too early and the round counts as a false start.
About ReactionTest
ReactionTest measures how fast you can react to a visual signal. The screen sits red for a random 1.5 to 4.5 seconds, then flips green — the moment you see the change, click. Five rounds, scored on the average reaction time in milliseconds. False starts (clicking while it's still red) cost a fixed 1000 ms penalty so you can't game it by spamming. Typical adult reaction time on a clean signal sits around 250 ms; under 200 ms is exceptional, and anything under 150 ms almost certainly means you anticipated the flip rather than reacting to it. Free, no account, plays on any device.
How to play ReactionTest
After the 3-2-1 countdown, the arena turns red. Hold steady — the screen will flip green at an unpredictable moment between 1.5 and 4.5 seconds later. The instant you see green, tap or click anywhere on the arena. Your reaction time appears with a verdict (Lightning, Sharp, Solid, Average, Slow). If you click while it's still red, that's a false start and the round counts as a 1000 ms penalty.
Tips for faster reactions
Don't anticipate the flip — your brain can pattern-match the random delay distribution and try to pre-fire, which is exactly how false starts happen. Keep your finger relaxed on the trigger, eyes loose on the screen, and let the colour change pull the click out of you instead of pushing it. A quiet room, low caffeine for the first try, and a wired mouse beat a touchpad by a few ms. Most reaction time research puts the human floor around 100-120 ms (signal travel + nerve transmission); you'll typically see your best honest score in the 180-220 ms range.