Wait for the screen to turn green, then click as fast as you can. Five tries, your average in milliseconds, false starts caught.
A reaction time test measures the milliseconds between the screen turning green and your click, and this one averages five tries into one number. Click the box to start. It turns red and says Wait for green. After a random wait of 1.5 to 4.5 seconds it turns green and says Click now. The clock starts just before that green is painted, and stops at your click. Green at 5000 ms and a click at 5250 ms is 250 ms. A round is five tries, and the average is the sum divided by five, rounded to a whole millisecond. Tries of 250, 240, 260, 230 and 270 ms average 250 ms, with 230 ms the fastest and 270 ms the slowest. The random wait changes on every try so you cannot count your way to it. The page also shows the fastest, the slowest and your list of tries, and keeps the finished rounds of this visit.
A click before the screen turns green is a false start. The box says Too soon, the try does not count, the false-start counter goes up, and your next click begins a new random wait for the same try. The left mouse button counts when you press it down, not when you release it. A tap on a touch screen counts the same way. With the box focused, Space and Enter also count once per press, and holding the key does not repeat. The right and middle mouse buttons and other keys are ignored. Comparing a keyboard score with a mouse score is not fair, so keep to one kind of input between rounds.
The score is the time the page measured, not only your nerves and muscles. It includes the screen and your input device. A 60 Hz screen redraws every 16.7 ms, so green can reach your eyes up to that much after the page asked for it, and a mouse that reports 125 times a second adds up to 8 ms to the click. A faster screen redraws every 8.3 ms at 120 Hz and 6.9 ms at 144 Hz. The display's own response time and the speed of your browser add more. For that reason a phone and a laptop give different scores for the same person, and a fair comparison uses the same device and the same kind of input each time.
There is no scale that calls a time good or slow, no ranking against other people, and no score table, because a number from one device means little for another. Nothing is saved: the tries and the last 10 finished rounds live in this tab's memory and are gone when you reload. Use the Reset button to clear them. The test needs the page to be in front. If the tab loses focus during a wait, start the try again.
From the moment the green is about to be painted to the moment your click or key press arrives, in whole milliseconds. Green at 5000 ms and a click at 5250 ms is 250 ms. The average of five tries is the sum divided by 5.
Any left click, tap, Space or Enter before the screen turns green. The box says Too soon, the try is not counted and the false-start counter goes up by 1. Your next click begins a new random wait of 1.5 to 4.5 seconds.
The screen and input device add time. A 60 Hz screen redraws every 16.7 ms, a 144 Hz screen every 6.9 ms, and a mouse reporting 125 times a second can add up to 8 ms. Compare scores only from the same device and the same kind of input.
The wait is random between 1.5 and 4.5 seconds, picked again for each try. If it were fixed, you could count to it and click on time instead of reacting. Clicking early is a false start.
Yes. Focus the box, then press Space or Enter for each step: once to start, once when it turns green. Holding the key does not repeat. Keep to one kind of input within a round, because a key press and a mouse click do not take the same time.
No. The times are measured in your browser, kept only in this tab's memory and gone when you reload, and no server receives them. The page counts visits with Google Analytics, never your clicks or times.