How is the time measured?

The page changes the pad on a screen frame and notes that frame's time, then subtracts it from the time your press arrived. Both come from the same high-resolution browser clock. The measurement is as good as your browser's timing, which is within about a millisecond, but the screen and input lag on top of it are not something a web page can see.

Why did it say Too soon?

You pressed before the pad turned green, or so quickly after it (under 80 ms) that the press must have started before green. That round doesn't count and runs again.

Why are my times slower on my phone?

Touchscreens usually take longer than a wired mouse to report a tap, and some phones wait briefly to tell a tap from a scroll. The page asks the browser not to wait, but the screen itself still adds time. Compare phone runs with phone runs.

A little. Practice, a good night's sleep and a few warm-up rounds all help, and so does a wired mouse. Most of the gain comes in the first few tries, as you get used to the test.

Where are my results saved?

Only in this browser, in its local storage: the last 20 runs of each mode. Nothing is sent to HourLife, and clearing your browser's site data or pressing Clear removes them.

Games
Brain tests
Reaction Time Test

Reaction time test

Wait for the pad to turn green, then tap as fast as you can. Five rounds give you an average; one round is a quick check.

Play full screen Your results

1 minute for five rounds
Mouse, touch or keys Space and Enter work too
No account your times stay in this browser

Results depend on your screen, browser and mouse or touch. Compare runs on the same device.

Your results

No runs yet. Take the test above and your scores appear here.

Kept in this browser only: your last 20 runs of each mode. Nothing is sent to HourLife.

How it works

Wait for green
The pad turns red and says Wait. After somewhere between one and a half and four and a half seconds, it turns green and says Tap. The delay is random, so you can't count it out.
Tap the moment it changes
Your time runs from the frame the pad turned green to the moment you pressed. Tapping before green reads Too soon, and that round runs again without counting.
Read your average
After five rounds you get the average and each round's time, with the fastest marked. Your last 20 runs of each mode are kept on this page, so you can see how a time moves.

What a reaction time measures

This is a simple reaction time: one signal, one response, no choice to make. The time covers your eyes noticing the change, your brain deciding it has happened, and the signal reaching your hand. Most of it is the deciding and the moving, not the seeing.

Healthy adults tend to land somewhere around a fifth to a quarter of a second on a test like this one, but the spread is wide, and the device matters as much as the person. A screen that refreshes 60 times a second can add up to 16 ms on its own, and a wireless mouse or a slow touchscreen adds more. That is why the page compares you only with your own runs on the same device.

Sleep, caffeine, attention and practice all move the number. A few rounds of warm-up usually help, and so does looking at the middle of the pad rather than at the edge.

Sources: Woods et al., Factors influencing the latency of simple reaction time, Frontiers in Human Neuroscience (2015).

Questions

How is the time measured?

The page changes the pad on a screen frame and notes that frame's time, then subtracts it from the time your press arrived. Both come from the same high-resolution browser clock. The measurement is as good as your browser's timing, which is within about a millisecond, but the screen and input lag on top of it are not something a web page can see.
What is a good reaction time?

There is no single answer, because the device adds a different delay for everyone. Many adults land around a fifth to a quarter of a second on a test like this. The fairer comparison is with yourself: take it a few times on the same device and watch the average.
Why did it say Too soon?

You pressed before the pad turned green, or so quickly after it (under 80 ms) that the press must have started before green. That round doesn't count and runs again.
Why are my times slower on my phone?

Touchscreens usually take longer than a wired mouse to report a tap, and some phones wait briefly to tell a tap from a scroll. The page asks the browser not to wait, but the screen itself still adds time. Compare phone runs with phone runs.
Can I get faster?

A little. Practice, a good night's sleep and a few warm-up rounds all help, and so does a wired mouse. Most of the gain comes in the first few tries, as you get used to the test.
Where are my results saved?

Only in this browser, in its local storage: the last 20 runs of each mode. Nothing is sent to HourLife, and clearing your browser's site data or pressing Clear removes them.