Reaction time test
Click to start; after a short pause the screen turns green. Click again at that moment and you get your time in milliseconds. The wait is different every round — a fixed wait would measure your sense of rhythm instead of your reaction. Your fastest time ever stays in this browser; the current five rounds start over when you leave the page.
The space bar works too
What is timed: from the green being drawn to the press
The moment the screen turns green is stamped with performance.now(), subtracted from the moment of the press and rounded to whole milliseconds. It is the browser's monotonic clock rather than the system clock, so a time correction mid-round cannot produce a negative result. The green still has to be painted before it reaches your eye, and at 60 Hz that can take up to 16 ms. So the number here is your reaction plus the display and input latency of the device, which is why comparing on the same machine is what makes sense.
The five bands
A one-line note is attached after each round. Under 200 ms is close to the limit of human visual reaction, 200–250 ms is quick, 250–320 ms is the common range, 320–450 ms is relaxed, and above that is a beat late. 231 ms is quick. No rank or percentile is given — the value moves by tens of milliseconds with the screen, mouse and browser, which makes it a poor ruler for comparing people.
Best, record and average are three different things
Best is the smallest of the five rounds in this run; average is the five added and divided by 5, rounded to a whole number. For 262, 231, 298, 251 and 244 ms the best is 231 and the average 1,286 ÷ 5 = 257. The record is kept in this browser's storage, so it survives a refresh or a visit next week, and it is checked after every single round rather than at the end of the run. Starting over does not erase it. Nothing is sent to a server.
An early press does not count, and the wait restarts
Press before the green and that round is void; the round counter does not advance. Pressing again starts a new wait, chosen at random between 1.2 and 4.2 seconds each time, so the rhythm cannot be memorised and a guess cannot manufacture a sub-100 ms record. The space bar follows the same rule. After five rounds no further round starts, and starting over clears only this run's times.
Common questions
QWhat is a typical time?
Seeing the change and moving a finger usually takes 200–300 ms. Below 200 ms is close to the limit of human visual reaction, and anything far faster means the click began before the green appeared. Those rounds are not counted here.
QDoes the device change the result?
Yes. A 60 Hz screen can add up to 16 ms before the green is drawn, and wireless mice and Bluetooth keyboards lag wired ones by a few milliseconds. Touch is generally slower than a mouse. That makes this more useful for watching your own numbers on one device than for comparing with other people.
QWhy five rounds?
One or two rounds are mostly luck, and past ten attention drifts so later rounds get slower. Five is enough that a single unusually fast or slow round does not dominate the average, while concentration holds. The best time is shown alongside because an average can be dragged by one slip.
QIs my score saved?
Only your single fastest time is kept, in this browser. Nothing is sent to a server, so it does not follow you to another device, and clearing site data removes it. The average of the current five rounds starts over on refresh. When you beat your best, the screen says so.
QWhat if I click before it turns green?
That round is void and the wait restarts. Counting an early click would measure guessing rather than the time it takes to see and react.