Speed and Precision
Wait on red, react on green. This simple test measures how quickly you respond to a visual signal, and how consistent you are from one try to the next.
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Example
The change from red to green happens in a single frame. The timer starts on the frame that shows green.
Timing starts from the frame where green is painted, and stops at your input event timestamp.
Simple reaction time has been studied since the 1800s and is still a basic measure of processing speed.
Use a mouse, a trackpad, a key or a touch screen. Compare sessions on the same setup.
Results never leave your browser. No account needed.
See your median, mean, best, worst and variability, plus a bar chart of every trial.
Early responses repeat the trial, so guesses never sneak into your average.
Your middle time across all valid trials. It is the main score because one slow trial cannot distort it.
How it is calculatedMiddle value of valid trial times
Your fastest trial shows your peak. The average shows your typical speed.
How it is calculatedMinimum and mean of valid trial times
How much your times spread out. Lower variability means steadier attention.
How it is calculatedSample standard deviation of trial times
Responses before green or within 150 ms of it. These are anticipations, not reactions.
How it is calculatedCount of early responses
These bands are site-defined guidance for adults on a desktop computer or a recent phone. They are not population norms and not a diagnosis.
| Band | Range | What it means |
|---|---|---|
| Exceptional | below 200 ms | Very fast, especially including device lag. |
| Fast | 200-249 ms | Quicker than most sessions. |
| Average | 250-299 ms | A common range for adults. |
| Below average | 300-349 ms | A little slower, often device related. |
| Slow | 350 ms or more | Check your device, and try when rested. |
In the nineteenth century the Dutch physiologist Franciscus Donders used reaction times to estimate how long mental steps take. His idea, that time reveals thinking, still shapes psychology today.
Simple reaction time, one signal and one response, is the most basic version of that measure.
Light reaches the eye, the retina converts it into signals, the visual cortex recognizes the change, and the motor system sends a command to your finger.
Each step takes a few dozen milliseconds. Together they add up to the quarter of a second that most adults need.
Screens refresh at fixed intervals, and mice, keyboards and touch screens have their own delays. Together they often add 20 to 80 ms.
That is why the same person can score differently on two devices. Compare your results on one setup only.
Age, sleep, caffeine, alertness and practice all matter. Reaction time is usually fastest in young adulthood and slows gradually afterwards.
Warming up helps. Many people are slower on the first few trials, which is one reason the median is used.
This test measures simple reaction time: one signal and one response. When a task asks you to choose between responses, such as left or right, reaction times grow longer because a decision step is added.
That is why simple reaction time is usually the fastest number you will see on this site, and why it is a useful baseline for comparing other tasks.
The wait before green varies between 1.5 and 5 seconds. If the delay were fixed, people would learn the rhythm and start moving before the color changed. A random delay makes anticipation much less useful.
Responses within 150 ms of green are still treated as false starts, because a genuine visual reaction that fast is very unlikely.
Two people with the same median can behave very differently. One gives steady times within a narrow range, while the other mixes very fast and very slow trials.
The variability tile shows this spread as a standard deviation. Lower values mean steadier attention, and tracking it over time can be just as interesting as tracking speed.
Reaction time is used to study alertness, aging, fatigue and the effects of substances such as caffeine.
A quick classroom experiment for teaching measurement, averages and variability.
Gamers, athletes and curious people use it to track alertness from day to day.
Reaction time tasks feature in some research batteries. This online test is not a medical assessment.
Keep the mouse button or key half ready so your movement is as short as possible.
The delay is random. Predicting the change leads to false starts.
Wired mice and fast displays usually add less delay than trackpads or older screens.
Run a Practice session first. Your Standard result will usually be steadier.
It measures how long it takes you to respond to a signal. Here the signal is the panel turning from red to green.
The panel turns red, then green after a random delay. You click, tap or press Space as soon as you see green. Your time appears, and the next trial starts when you continue.
Practice has 5 trials, Standard 10 and Challenge 20. Most sessions take one to two minutes.
Yes. Press P, use the pause button, or switch tabs. The current trial restarts with a new delay. Stop shows a result once you have 3 valid trials.
Any modern browser. A desktop with a wired mouse gives the lowest delay.
The median is your typical speed. Best is your peak, and variability shows how steady you were. False starts are counted separately.
Many adults score between 250 and 300 ms on this kind of test, including device lag. Below 200 ms falls in the site's Exceptional band.
Use History in the menu, or View history after a session.
Only in your own browser. Nothing is sent to a server.
Reload the page. If clicks seem ignored, make sure the test area has focus and that no other program is using a lot of processing power.
Touch screens and phone displays often add more delay than a wired mouse and a desktop monitor. Compare results only on the same device.
Use the median. A single fast trial can be partly luck, while the median reflects your typical speed across the whole session.
Results depend on age, device, sleep, language, mood and practice. Average several sessions before drawing conclusions. This is not a medical or psychological diagnostic tool.
It takes about a minute. Your results stay private in this browser.