Reaction Time Test
Wait for the panel to change, then respond as fast as you can. Repeat for several rounds to get your average.
5 rounds. If you respond before the stimulus, that round is repeated.
How it works
- Press Start test.
- Wait for the panel to change and show “Click now!”.
- Respond as fast as you can: click, tap or press Space.
- Repeat for all the rounds. If you respond too early, that round is repeated.
- Get your average, best and worst times.
What does this test measure?
It measures the time between a visual stimulus shown by this page and the moment your browser receives your response (a click, a tap or the Space key). It is not a measurement of your pure biological reaction time.
The result also includes, and can be affected by:
- Your screen (refresh rate and display latency)
- Your input device (mouse, trackpad, touchscreen or keyboard)
- Your browser
- Your operating system and how it processes events
This is a browser-based measurement, not a clinical or laboratory one. The clock starts when the stimulus is added to the page and stops when the browser receives your press, so display and input delays are included. Compare results only between attempts on the same device and browser. Your best average is stored only in this browser.
What happens in each round
A round starts with a random wait of 1.5 to 5 seconds. The delay is drawn so that two waits in a row are never too alike, which stops you from learning the rhythm and anticipating it. When the wait ends the panel changes and the clock starts; your first click, tap or press of Space stops it. Five valid rounds make a run.
If you respond before the panel changes, that round doesn't count: you see “Too early”, the false-start counter goes up and the round is repeated after a short pause. Responses in the first 0.4 seconds of a wait are ignored, so a double click on Start test isn't counted as a false start. If you switch away from the tab in the middle of a round, that round is discarded and starts again when you come back.
How the time is taken
The clock starts when the page adds the stimulus to the screen, and the browser paints it right afterwards, so that short delay is inside your time. It stops when the browser receives your response. On a 60 Hz display a new frame appears about every 16.7 milliseconds, so what you see can show up to roughly one frame after the clock starts, and a mouse, a trackpad or a touchscreen each add their own small delay.
Reading your average, best and worst
| Number | What it tells you |
|---|---|
| Average | The mean of your five valid responses. It's the headline figure and the one stored as your best average. |
| Best | Your fastest single response: the quickest your whole chain of eyes, hand, input device and screen managed once. |
| Worst | Your slowest response. A big gap between best and worst means the run was uneven; distraction or the input device are the first things to rule out. |
| False starts | How many times you responded before the stimulus. A high count means you were guessing rather than reacting. |
Your best average is stored in this browser only, so it helps you compare your own attempts on this device and nothing more.
A worked example
The numbers below are invented to show how to read a run; they aren't typical values or a target. After the five valid rounds the page lists each round in whole milliseconds and works out the summary from them:
| Round | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Time (ms) | 231 | 247 | 226 | 262 | 239 |
The five times add up to 1,205 ms, so the average is 241 ms. The best round is 226 ms and the worst is 262 ms, a spread of 36 ms. On its own the 241 doesn't say much. What is worth watching across several runs is whether the average settles and whether the spread narrows or widens, because a run with one very slow round (a lapse of attention, a notification, a stiff mouse button) drags the average up without meaning your reactions changed.
What can and can't be compared
The figure contains more than your reflexes: the screen's refresh and processing delay, the input device, the browser and the operating system all sit inside it. Two people on different setups, or the same person on a different device, can't be compared fairly, and the result is not a clinical or laboratory value. What it is good for is comparing your own attempts on the same device, browser and input method. The guide on what browser tests can and can't measure explains why a web page can't separate those parts.
What to do next
For a steadier picture, run several attempts and look at your best averages rather than a single run, resting between them and using the same input each time. If you suspect the screen is part of the delay, the Refresh Rate Test estimates how often your browser draws frames. The Click Speed Test shows how fast you can repeat an action, which is a different skill from responding to a cue.