How to take the reaction time test
- Click the box, tap it, or press Space. It turns red: wait.
- After a random wait of 1.5 to 5 seconds it turns green. Click, tap or press Space as fast as you can.
- Your time appears in milliseconds (ms) — thousandths of a second. Click again for the next try.
- After five tries you see your average and your best time, and the list of all five. Click once more to start a new round.
Clicking while the box is still red shows Too soon!: that try doesn’t count, and you simply try again. Because the wait is random, you can’t learn the rhythm — you have to react to the color.
How the time is measured
The page changes the box to green and starts the clock in the same screen frame. Your click, tap or key press carries its own timestamp from the browser’s high-resolution clock, and your reaction time is the difference between the two. The random wait uses your browser’s cryptographic random-number generator.
What you measure is the whole chain from light to click: your eyes see the color change, your brain decides, your finger moves — plus the delay of your equipment. A 60 Hz screen draws a new frame every 16.7 ms (1,000 ÷ 60) and a 144 Hz screen every 6.9 ms; a mouse reporting 125 times a second adds up to 8 ms, one reporting 1,000 times a second up to 1 ms; wireless connections, touchscreens and power-saving modes can add more. That is why results are best compared on the same device.
Example
Five tries of 268, 245, 301, 252 and 259 ms add up to 1,325 ms. The average is 1,325 ÷ 5 = 265 ms, and the best try is 245 ms. The average tells you more than the best try: one lucky guess that happened to land just after the change can make a single try look very fast.
What is a normal reaction time?
In laboratory conditions, a 2015 study in the International Journal of Applied and Basic Medical Research (Jain, Bansal, Kumar and Singh) gives about 190 ms as the accepted mean simple reaction time of college-age people to a light, and about 160 ms to a sound, citing the reaction-time research of A. T. Welford. Lab equipment has almost no delay of its own, so results in a browser — with a screen, a mouse and an operating system in between — normally come out higher. The same study found that reactions to sound were faster than to light, and that students who exercised regularly reacted faster than sedentary students. It lists age, practice, fatigue and fasting among the factors that change reaction time.
Tips for a fair result
- Use the same device, screen and mouse each time; a wired mouse and a high refresh rate screen add the least delay.
- Close other heavy tabs and apps, and don’t test on a laptop in battery-saver mode.
- Rest your finger on the button or the Space bar, look at the box, and keep the page in front.
- Do a full round of five and compare averages, not single tries. Your times will vary from try to try — that is normal.
- Test at different times of day: a tired or distracted brain is slower.
This test is for fun and practice. It is not a medical test and not a test of fitness to drive. Measure your clicking speed with the CPS test or your typing with the typing test.
Frequently asked questions
What is a good reaction time?
Laboratory studies put the average simple reaction time of young adults to a light at about 190 ms (Jain et al., 2015, citing Welford). In a browser, your screen, mouse and system add their own delay, so typical results here are higher — compare your own averages on the same device rather than with lab figures.
Why is my reaction time slower on my phone?
Touchscreens, power-saving modes and the way phones process taps can add delay before the browser receives your touch. Results on different devices are not directly comparable.
Why does clicking too early not count?
A click before the box turns green is a guess, not a reaction. The try is discarded and you start it again; the random wait of 1.5 to 5 seconds makes guessing the moment impossible.
Can I improve my reaction time?
Practice with a task usually makes you faster at that task, and being rested and alert helps. In the study cited above, students who exercised regularly had faster reaction times than sedentary students.
Is my data saved?
No. Your times are kept on this page only while it is open; nothing is sent to a server.
Last updated: October 15, 2026