Reaction Time Test — Measure Your Reflexes in Milliseconds
Free reaction time test. Click the moment the box turns green and see your reflexes in milliseconds, with the best, median and consistency across five trials. Three modes: visual, Go/No-Go and audio. No sign-up; records stay in your browser.
Typical reaction times (visual)
Commonly cited reference points for a simple reaction to a colour change. Comparing your median is the easiest way to place yourself.
| Reaction time | Rating | Reference |
|---|---|---|
| Under 180ms | Exceptional | The level reported for esports players and F1 drivers. Very few people hit it consistently. |
| 180–219ms | Very fast | Common among people who play action games regularly. |
| 220–269ms | Fast | A little quicker than average — roughly where you land when fully focused. |
| 270–339ms | Average | Said to be where most adults fall for a visual reaction. |
| 340ms and over | Slow | Drowsiness, fatigue or a laggy display will push you here on their own. |
These bands are rough reference points drawn from commonly cited figures, not an official statistical standard or a medical benchmark. Do not use your reaction speed to judge your health.
What a reaction time test measures
A reaction time test measures, in milliseconds, how long it takes from the moment a signal appears to the moment your body responds. Here you click the instant a red box turns green, and the gap is timed with performance.now(), the browser's high-resolution clock. A single trial is dominated by luck, so a session runs five of them and reports the best, the mean, the median and the spread together.
Strictly speaking this is not a biological reflex. A knee-jerk completes in the spinal cord in roughly 0.05 seconds; looking at a screen and clicking involves visual processing, a decision and a motor command, so it takes four or five times longer. What people mean by "good reflexes" in everyday speech is the latter, and that is what this tool measures.
How to use the reaction time test
- Pick a mode Start with "Visual (colour change)" if this is your first time. Once you are comfortable, try Go/No-Go, which adds a decision, or the audio mode, which responds to sound.
- Click the panel to begin A click or the space bar starts it. The wait before the signal varies randomly between 1.2 and 4.5 seconds, so you cannot time your press in advance.
- Press the moment it turns green Pressing before the signal is logged as a false start and that trial produces no time. Mouse or space bar both work, but swapping halfway changes your conditions.
- Finish five trials and read the result You get the best, median, mean and spread. To judge your ability, weight the median over the mean — it is far less sensitive to one bad trial.
Tips for getting more out of it
- Read the median rather than the mean. One slow trial out of five drags the mean down by tens of milliseconds while barely moving the median, which sits much closer to your steady ability.
- A smaller standard deviation is better. Two people with the same best time can differ a lot in consistency — the one with the wider spread had trials where their attention slipped. Fatigue shows up here first.
- Some people are quicker with the space bar than with a mouse click, because the travel and the finger movement differ. Which one wins depends on your hardware, so keep the conditions fixed when you compare.
- External monitors can lag behind a laptop's built-in panel. The same person can move by tens of milliseconds after changing screen or cable, so keep your records on one setup.
- Go/No-Go is always slower than a simple reaction, and that is normal. The extra time is the decision itself. Judge that mode by how few errors you make, not by speed.
When this is useful
Compare a gaming setup before and after a change
Switching refresh rate, turning on a monitor's game mode or moving between a wired and wireless mouse can be checked as a number rather than a feeling. Human reaction changes little, so any difference is largely down to the equipment.
Gauge your own drowsiness or fatigue
Reaction time and its spread both degrade with poor sleep. Measuring in the morning and again late at night puts a number on how your focus falls away (this is not a medical assessment).
Compete with friends and family
Taking turns on the same device with the same input gives a genuinely fair comparison. Records are kept per mode in the browser so you can revisit them.
Use it as an attention task
Go/No-Go is a classic psychology paradigm for measuring the ability to withhold a response. It tests you on a second axis: not just pressing fast, but managing not to press on blue.
Terms used on this page
- Reaction time
- The interval between a signal appearing and your body starting to move. It covers sensory processing, the decision and the motor command. This is the figure the tool displays.
- Simple reaction time
- Reaction time when there is only one signal and you always respond to it. The visual and audio modes here are of this kind.
- Go/No-Go task
- A task mixing signals you must respond to (Go) with signals you must not (No-Go). Because it measures sustained attention and impulse control at once, it is widely used in psychology and neuroscience.
- False start
- Responding before the signal appears, which happens when you anticipate it. The trial produces no valid time — the same idea as a false start in athletics.
- Median
- The middle value once the results are sorted. Because one very slow trial barely moves it, it reflects ability better than the mean.
- Standard deviation
- How spread out the values are. Smaller means you reacted at a more consistent speed, which reflects how steady your attention was.
- Input lag
- The delay between pressing a mouse or key and that signal reaching the computer and showing on screen. It is always included in the measurement.
Frequently asked questions
Side Note — Measuring reaction time began with astronomers and their "personal equation"
Reaction time first came under serious study not in psychology but in astronomy. In nineteenth-century observatories, an astronomer would watch a star cross a reference line in the telescope and record the moment while counting seconds by ear. Yet the same star, seen through the same instrument, produced slightly different times depending on who was watching. In the 1820s the Königsberg astronomer Friedrich Bessel documented this carefully and showed that each observer ran consistently early or late by their own amount. The correction became known as the personal equation.
At first this was purely a nuisance — an error to be subtracted away. By the second half of the century, though, the error itself had become the subject. If mental work took measurable time, it could be timed, and the Dutch physiologist Franciscus Donders set out to isolate the act of deciding by varying how many signals an observer had to tell apart. Subtract the simple reaction from the discriminating one, he reasoned, and what remains is the time spent judging. The Go/No-Go mode here inherits that subtraction directly.
Today the measurement quietly shapes ordinary life. Calculations of stopping distance for a car allow roughly 0.75 seconds of "thinking distance" between recognising a hazard and touching the brake — far longer than the 0.25 seconds of a simple reaction, because it includes judging the danger and moving a foot from one pedal to the other. Reaction time may sound like a matter of milliseconds, but at 60km/h one second carries you about 17 metres.
The awkward part has never really been solved: the figure always includes the apparatus. In Bessel's day the apparatus was a human counting seconds aloud; in a browser it is the screen refresh cycle and the input device. Just as nineteenth-century astronomers corrected for each observer's habits, we fall back on the same plain remedy — keep measuring on the same setup.