Five-trial test
Ready for a reaction-time trial.
Results
How timing works
A randomized 1.5–4 second wait prevents a fixed rhythm. The green stimulus is timestamped with performance.now() on its presentation frame; your response uses the same monotonic clock.
Interpretation limits
This browser test includes display, input-device, operating-system, and scheduling latency. It is not a medical, neurological, concussion, driving, or athletic assessment.
Accessibility and privacy
Controls are keyboard accessible, status changes are announced without per-frame live-region noise, and reduced-motion preferences disable decorative motion. No account, leaderboard, cloud history, or remote processing is used.