Reaction Time Test
When the box turns green, click (or tap, or press Space) as fast as you can. Five attempts.
What is a good reaction time?
For a visual stimulus, the average adult responds in roughly 250 milliseconds. Under 200 ms is very quick; over 300 ms is slower than average. Results depend on your screen refresh rate, mouse or touch latency, tiredness and focus, so treat the number as a fun benchmark rather than a medical measurement.
Tips for a better score
- Use a mouse or keyboard on a screen with a high refresh rate.
- Keep your finger resting on the button.
- Do not click early — it counts as a false start and the attempt restarts.
FAQ
Why is my score different from other sites?
Each device adds its own delay between your click and the browser registering it. Compare scores on the same device over time.
Is my score stored?
No. Nothing is uploaded; the result lives only in this page.
Taking the test
- Click the blue box (or tap it, or press Space or Enter while it is focused). It turns red and says "Wait for green...".
- Keep your finger ready. After a random pause the box turns green and reads "CLICK NOW!". Respond as quickly as you can.
- Your time in milliseconds appears under "Last". Click again to start the next attempt.
- After five attempts the box shows your average. The panel below tracks the last result, the running average, your best single time and the attempt count. Click once more to begin a fresh set.
What is being measured
The timer starts the moment the box turns green and stops when the browser receives your press. It reads the page's high-resolution clock, performance.now(), and rounds the difference to the nearest millisecond. The test listens for the press itself (mouse button down, touch start or key down) rather than waiting for the release, so the time you spend lifting your finger is not counted.
The wait before green is random, between about one and four and a half seconds. The randomness matters: if the delay were fixed, you could learn the rhythm and click on anticipation instead of on seeing the change.
A worked example
Suppose your five results are 243, 261, 228, 275 and 250 ms. They add up to 1,257, and divided by five that is 251.4, which the tool shows as an average of 251 ms. Your best is 228 ms. Notice that the spread between fastest and slowest is nearly 50 ms. That is typical for a person, so a single result tells you less than the average does, and it is why the test asks for five attempts.
False starts
If you click while the box is still red, you get "Too soon!" and no time is recorded. The next click begins a brand new set, so results from earlier attempts in that set are cleared. This discourages guessing: pressing early and hoping to land on the green moment does not give you a faster score, it only costs you the set.
What affects your number
- Your body: alertness, sleep, caffeine, age and practice all play a part. The first attempt of a session is often slower than later ones, though this varies between people.
- Your display: a screen redraws a fixed number of times per second. On a 60 Hz monitor a new colour can appear up to about 17 ms after the page requested it, whereas a 144 Hz monitor cuts that wait to about 7 ms.
- Your input device: wired mice, wireless mice, trackpads, keyboards and touchscreens each add different delays, and touch screens usually add more.
- Your browser and system load: a busy computer with many tabs open may respond a little later.
Getting consistent comparisons
Because device delay is built into every number, comparing your score with a friend's on another computer says little. Compare yourself against yourself: same device, same input method, similar time of day. Close other heavy tabs, stay seated the same way, and run a few full sets before drawing conclusions. If you want to see the effect of something, such as a coffee, test before and after with the same setup.
Common uses
- A quick warm-up or break-time game with friends, comparing averages.
- Classroom science demonstrations about reflexes and the nervous system.
- Seeing how tiredness changes your results across a long day.
- Checking whether a different mouse, keyboard or monitor feels faster in practice.
Limits
- The result is a measure of visual reaction with a particular device. It is not a medical, driving-fitness or sports-science test.
- Only one kind of signal is used, a colour change. Reaction to sound or touch can differ.
- Nothing is saved between visits; refreshing the page clears all results.
- Very small differences of a few milliseconds are within the noise of the setup and should not be over-interpreted.
More questions
Why is the average so much higher than my best time?
One lucky attempt can be far faster than your usual. The average includes slower tries where attention dipped, so it is the better indicator of your typical response.
Can I use the keyboard instead of the mouse?
Yes. Click the box once to focus it, then use Space or Enter. Many people find keys slightly faster than a mouse, but results depend on the keyboard.
Is it possible to score below 100 ms?
Not by reacting honestly to the colour. Human visual reaction involves detecting the change, deciding and moving a finger, and that takes longer. A suspiciously low number usually comes from anticipating, which the random delay is designed to make unreliable.