Reaction Time Test

How to take the test

1. Click or tap the big box, or press Space. The box turns red and says Wait for green….
2. After a random wait of 1.5 to 5 seconds, it turns green and says GO! Click!. Click, tap or press Space or Enter as fast as you can.
3. Your time appears in milliseconds. Click again for the next try.
4. After 5 tries, the box shows your Round average. Click once more to start a new round.

If you react before the box turns green, you get Too soon! and that try does not count: the random wait makes guessing useless. New round discards the current round, and Clear history erases your saved results and records.

Reading your results

• Last is your most recent try; Round average is the mean of the tries in the current round.
• Best try and Best average are your personal records, kept in this browser.
• The histogram under Your reaction times shows how your last 200 tries are spread, in 25 ms bins (anything slower than 600 ms goes into the last bin). The darker bar contains your latest try. A narrow, tall peak means consistent reactions; a wide spread means your attention varies. The summary above the chart gives the median and the standard deviation (the “±” spread).

Most adults score between about 200 and 300 ms on a visual test like this one, and averages around 250 ms are typical. Values under 150 ms are rare and usually mean a lucky anticipation rather than a real reaction.

What the time really includes

The number measures the time between the moment the page starts drawing the green box and the moment your browser receives your click or key press. It is a little longer than your pure nervous-system reaction because of the equipment in between:

• Display latency. A 60 Hz screen shows a new image every 16.7 ms, and many monitors and TVs add processing delay on top. A 120 Hz or 144 Hz gaming monitor with low input lag shows the green sooner.
• Input latency. A wired mouse or keyboard typically adds 1 to 10 ms. Wireless devices, Bluetooth and touch screens often add more; touch screens can add several tens of milliseconds.
• Browser and system load. A busy computer, power-saving mode or many open tabs can delay events slightly.

The test uses the high-resolution performance.now() clock and the event’s own timestamp, and it reacts to the press (not the release) of the button, so it adds as little as possible on its side. Still, compare your results only on the same device: a phone and a desktop can differ by 30 ms or more for the same person.

How to improve your reaction time

• Sit comfortably, keep your finger resting on the mouse button or the Space bar, and look at the centre of the box.
• Sleep, caffeine, warm-up and practice all make a measurable difference; fatigue and distraction make you slower and less consistent.
• Judge progress on the average and the median, not on a single lucky best try.