How Millisecond Reaction Speed Testing Works
Millisecond Reaction Speed Test runs entirely in your browser with JavaScript. There is no sign-up, and whatever you type or open here is processed on your device instead of being sent to a server.
Measure Your Visual Reflexes with Millisecond Precision
Test how quickly your brain responds to visual color changes from red to green. Timing uses the browser's high-resolution clock (performance.now): it starts with the animation frame that turns the box green and stops as soon as your finger, mouse button or key goes down, so your screen, mouse and browser still add a few milliseconds.
Keyboard and Touch Control Accessibility
Play by clicking with your mouse, tapping a touch screen, or pressing the Spacebar or Enter key on your keyboard. Keyboards and mice each add their own small delay, so compare results made with the same input method.
Saved Personal Best in Your Browser
Your fastest reaction score is preserved locally in your browser memory (localStorage) across page reloads without sending any personal metrics to external servers.
Why processing in your browser matters
Many online tools upload your files or text to a server to process them. This one does the work on your computer or phone, so your data is not sent to us or stored anywhere else. That lowers the risk when you work with confidential material, although you should still follow your organisation's own rules. Read how this works in our Privacy Policy.
- No uploads: files are opened and saved on your device, so there is no upload or download wait.
- No account: nothing to sign up for or install.
- Free to use: no subscriptions or paywalls.