Reaction Time Test (Click When It Turns Green)

About the Reaction Time Test (Click When It Turns Green)

Measure how fast you react. Start the test, wait while the pad is red, and the moment it turns green, click, tap or press Space or Enter. The wait is random each time, so it cannot be guessed, and a press before the green is caught and that round is run again. After five rounds you get your average, median, fastest and slowest round and how much they vary. With Sound the signal is a short beep instead, which also makes the test usable without seeing the screen.

Timing uses the browser’s high-resolution event time stamps against the first animation frame after the colour changed, and the page shows your screen’s measured frame interval, because no page can time a reaction more finely than the screen shows it. Your runs are kept only in this browser, with a chart of your averages: the page compares you with yourself, not with made-up averages of other people.

Common uses

• Checking your reaction time before and after practice, a game session or a good night’s sleep.
• Comparing two mice, keyboards or screens with the same test.
• A quick game with friends or in class — on one device, so the times compare fairly.
• Trying the sound signal to see how you react to a beep rather than a colour.

What the number includes

The time shown is from the moment the green appeared to the moment your press reached the browser. Besides your own reaction it includes:

• The screen: a change appears on the next frame the screen shows. The result panel gives your screen’s measured frame interval — about 16.7 ms at 60 Hz, 8.3 ms at 120 Hz.
• The input device: mice and keyboards report presses a few milliseconds late, wireless ones and touch screens often more.
• For the sound signal: the time the browser says the beep leaves the speakers; Bluetooth headphones and speakers add a delay of their own on top.

So compare times measured on the same device with the same signal; a faster screen or a wired mouse can take milliseconds off without any change in you.

Getting a fair result

• Do a practice run first: the first round is often slower.
• Keep your finger resting on the button or key, and look at the middle of the pad.
• Choose a quiet moment: tired, distracted or cold hands are slower.
• Use the same device, browser and signal when you compare runs; the page keeps colour and sound runs apart in your bests.

How the test avoids guessing and flashing

The wait before each signal is a random 1.5 to 4.5 seconds, drawn fresh for every round. A press during the wait, or less than 100 ms after the signal (faster than a real reaction), runs the round again and is counted as a too-soon press. The pad changes colour only when a round starts, at the signal and when you press, and never more than three times in any one second, the threshold of the WCAG 2.2 flash guideline: a press that would make it change faster is ignored. There are no animations.

Limitations

• A browser cannot see the light leave the screen: the green is timed from the first animation frame after it was drawn, which is close to, but not exactly, when it appeared.
• Results depend on the device as much as on you, so they compare fairly only on the same device.
• There is no official average reaction time this page could compare you with, so it shows only your own statistics.
• This is a game and a self-check, not a medical or driving-fitness test.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.