Reaction Time Test
Click the moment the stage changes colour, five times. A best of five is the luckiest trial rather than the typical one, so this page leads with the median of the five and keeps every trial on screen beside it. The wait before the signal is drawn at random from one to five seconds, or two to eight if you want it harder to anticipate, and a trial that cannot be a reaction is refused rather than scored: a response that arrives before the signal is a false start with nothing to react to, and a trial during which the tab stopped being visible is voided, because a browser stops painting a hidden tab and the elapsed figure would be the time it took you to come back. Timing runs on the browser's high-resolution clock, from the frame the colour was drawn in to the moment the press is reported, and the press is what counts rather than the release. The space bar and Enter work as well as a click or a tap. Nothing is uploaded and there is no account: your times and the wait range you chose stay in this browser.
The stage takes a click, a tap, the space bar or Enter, and the press is what is timed, not the release. A second press in the moment after a trial ends is ignored, so a double press cannot start the next trial while you are still reading the last one. Changing the wait range cancels a trial that is waiting; the trials already recorded stay. Your times and the range you chose are kept in this browser and nowhere else. If you are using a screen reader, the signal is announced after it is painted, so the reading will be higher than what your hand did.
Common questions
- What is a normal reaction time?
- There is no single number this page can hand you that would mean the same thing on your hardware and on someone else's. What it measures is the whole loop: your screen drawing the change, your eye and hand, and your browser reporting the press, and the screen and the input path are a real part of that figure on any machine. Nothing is uploaded from this page, so it also has no population of visitors to compare you against and does not invent one. The comparison that does hold is your own: run the five trials on the same machine on different days, or before and after a change to your setup, and compare the medians.
- Why does it report a median instead of my best time?
- Because the best of five is the luckiest trial, not the typical one, and it is the one figure a guess can buy: press a moment before the signal and, if it lands just after, you get a very low number that says nothing about how fast you react. The median is the middle of the five sorted times, so one lucky trial cannot move it and neither can one distracted one. Both are shown, the median first. If you stop before the fifth trial, the median of an even number of trials is the mean of the two middle ones.
- Does my screen or mouse affect the result?
- Yes, and nothing is deducted for either. A trial is timed from the frame the colour was actually drawn in to the moment the browser reports your press, so the refresh rate of the display, the response time of the panel and the polling rate of the mouse or the touchscreen are all inside the figure. That is why the accuracy line calls it comparable between your own runs on one machine rather than against a laboratory instrument. Some tests subtract a fixed number of milliseconds for display lag; that is a guess about hardware a web page cannot see, so this one does not.
- What happens if I click too early?
- It is a false start. The trial is not recorded, the stage says what happened, and you press again to run that same trial. A response that lands at the exact moment of the signal counts as early too, because there was no drawn frame before it to react to. False starts are counted on screen for the run, so a run with three of them is visibly a run with three of them rather than a suspiciously fast median.
- Why was one of my trials thrown away?
- Almost always because the tab stopped being visible during it, which is the one case the page voids on purpose: a browser stops painting a tab that is not on screen and holds its timers back, so the signal you would have reacted to was never drawn and the elapsed figure would be measuring your return to the page. Two other trials are refused rather than recorded: a response that lands more than ten seconds after the signal, which is somebody who looked away rather than somebody reacting, and the rare case where the clock does not give a usable pair of readings. In every case nothing is added to the list and the message says which it was.
- Where are my times kept?
- In this browser, on this device, and nowhere else. The trial times and the wait range you chose sit in local storage under one key; there is no account, nothing is sent anywhere, and no result of yours reaches any analytics. The Start over button at the top of the page clears them, and so does clearing site data. If your browser blocks storage, the test still runs exactly the same way and simply forgets between visits.
Timed with the browser's high-resolution clock, to the millisecond it reports. The figure includes your screen drawing the change and your device registering the click, so it is comparable between your own runs on one machine rather than against a laboratory instrument.