About Reactzy

Reactzy is a free reaction time test that runs in any browser, on a phone or a computer. There's nothing to download and you don't need an account to play. Wait for the green target, tap it as fast as you can, and after five rounds you get your average in milliseconds, along with the animal that matches your speed. Sign up if you'd like your best score on the global leaderboard.

Who makes it

Reactzy is a one-person project, built and run by Harcharan Singh. The aim was a reflex test that loads instantly, feels right on a touchscreen, and has a leaderboard people can trust. The guides dig into the science behind the numbers, from how reaction time changes with age to why it takes so much longer to brake a car than to tap a screen.

Keeping the leaderboard fair

Every score is checked on the server before it's accepted. The server, not your browser, decides when each target appears, so it knows the fastest a game could possibly be finished. A score doesn't count if any round was faster than 100 ms (the same false-start limit used in sprinting), if the game finished sooner than its targets could physically have appeared, if the timings look too machine-perfect to be human, or if the same game is sent twice. And only a tap or click on the target itself counts as a hit.

No online game is completely cheat-proof, so I also keep an eye on the top of the leaderboard and remove scores that don't add up.

Why there are ads

Playing is free, and ads cover the cost of running the servers. They stay out of the way: at most a short break between games, never in the middle of a round. The privacy policy explains how advertising cookies work.

Credits

Animal icons by Lorc, Delapouite and contributors at game-icons.net, licensed under CC BY 3.0. Interface icons from Lucide. Animations powered by Motion.

Contact

Found a bug, spotted a score that looks fishy, or want your account deleted? Email contact@reactzy.com.