How the test works
Choose 3, 5 or 10 attempts and press Start. The screen goes dark and asks you to wait. After a random pause between 1.5 and 4.5 seconds it turns bright yellow, and from that moment the clock runs until you tap the screen, click the left mouse button or press Space or Enter. The time appears in the middle of the screen; tap again for the next attempt. After the last counted attempt the screen closes by itself and the result card shows your average in milliseconds, your fastest and slowest attempt and your record for that number of attempts on this device.
Three kinds of attempts do not count and are repeated:
- Too soon. A press during the wait, or less than 100 ms after the light, is a false start. Nobody reacts that fast to something they see; it is a guess. False starts are listed in the result so you can see how often you jumped.
- Too slow. A reaction over 2 seconds is not counted, because you looked away and one long attempt would ruin the average.
- Paused. If you switch tabs or the phone locks during an attempt, that attempt is void.
Esc or the × button leaves before the last attempt without a result, since an average of two attempts out of five is a different test.
What the result means
The number is the time from the frame that lit the screen to the moment the browser received your press. That includes more than your nervous system: the screen needs time to show the frame, the mouse, keyboard or touchscreen needs time to report the press, and the browser needs time to pass it on. A 60 Hz screen alone can add up to 17 ms, a wireless mouse or a TV without game mode more. That is why the result is marked approximate and why it is best compared with itself on the same device.
- Under 200 ms. Very fast. Typical of rested, practised players on a good setup.
- 200 to 300 ms. The normal range for adults in a visual test.
- 300 to 400 ms. Slower than average. Check the setup below before blaming yourself.
- A large gap between fastest and slowest. Attention is drifting. Ten attempts give a steadier average than three.
For scale: a car at 50 km/h covers about 14 m per second, so 250 ms is roughly 3.5 m before your foot even starts to move. Braking in real traffic takes much longer than this test, because you also have to recognise the danger and decide.
How to get a reliable result
Sit so the whole screen is in view, rest a finger on the button or the screen and look at the centre. Use a wired mouse or the laptop touchpad rather than a Bluetooth device, close other heavy tabs and, on a TV, switch on game mode. Do a few warm-up rounds: the first attempts of the day are usually the slowest. Sleep, caffeine, alcohol and age all change reaction time by tens of milliseconds, so a single result says little; the trend over several days says more.
When the setup is slowing you down
If your average is much slower here than your reflexes feel, test the chain. The refresh rate test shows whether the browser really gets the frame rate your screen promises, and the mouse test shows whether the mouse is dropping or delaying clicks. A result that improves by 30 ms or more when you switch from a phone to a computer, or from a wireless to a wired mouse, is the device, not you.
Frequently asked questions
What is a good reaction time?
For a simple visual test like this one, most adults average between 200 and 300 ms, and large online tests put the typical result at around 250 ms. Below 200 ms is fast and usually belongs to young, rested people who play fast games. An average above 350 ms often means a slow device in the chain, a tired evening or a distraction rather than slow reflexes.
Why is my result slower on the phone than on the computer?
A touchscreen scans for fingers a limited number of times per second and the phone then has to process the touch, which can add a few dozen milliseconds that a wired mouse does not. The screen of a phone may also run at 60 Hz while a gaming monitor runs at 144 Hz. Compare results on the same device, not across devices.
Why did the test say too soon when I reacted to the light?
A press less than 100 ms after the light is counted as a false start, because that is faster than the eye, brain and hand can work together. It almost always means the press was started before the light, as a guess. The same happens when you press during the wait. The attempt repeats and the false start is shown in the result.
Does the test know if I guessed?
It cannot read your mind, but it makes guessing unprofitable. The wait before the light is random, between 1.5 and 4.5 seconds, so the moment cannot be learned, and every press before the light or within 100 ms of it is thrown out. A reaction slower than 2 seconds is not counted either, because you were clearly looking elsewhere.
Is my reaction time stored anywhere?
Only your best average for each number of attempts, in your browser's local storage on this device. It never leaves the device and there is no leaderboard. Clearing site data or using a private window removes it.