What your reaction time means
The number you see is the time between the moment the green screen is drawn and the moment your click, tap or key press reaches the browser. It is not only your brain and fingers: every result also includes the delay of your display (the time it takes a frame to become visible pixels) and of your input device (how quickly the mouse, keyboard or touchscreen reports the press). That is why the same person can score noticeably differently on a gaming monitor with a wired mouse than on a phone.
Simple visual reaction tests run in a browser commonly land somewhere in the region of 200–300 ms for alert adults, with plenty of normal variation either side. Treat that range as a loose guide rather than a grade: compare your results with your own earlier scores on the same setup. Any response faster than 100 ms is treated as a guess and does not count — that is the same 0.1-second limit World Athletics uses to detect false starts, because genuine human reactions to a signal are not that fast.
The round shows the average and the median. The median ignores one unusually slow or fast attempt, so it is often the fairest single number. A small spread (the ± value) means you are reacting consistently.
How to use the reaction time test
- Click, tap or press Space on the test area to start. The screen turns red — keep still.
- After a random wait of 1.5 to 5 seconds the screen turns green. Respond as fast as you can with a click, tap, Space or Enter.
- Your time appears immediately. Respond again to start the next attempt. If you go before green, the attempt is marked “too soon” and simply repeats.
- After five attempts you get the average, median and best, and your personal bests are saved in this browser.
What affects your score
- Refresh rate. A 60 Hz screen draws a new frame every 16.7 ms; a 144 Hz screen every 6.9 ms. Faster refresh means the green appears sooner after it is requested, which can shave several milliseconds off every attempt.
- Display processing. TVs in particular may add tens of milliseconds of image processing. Switching a TV to its game mode usually reduces it.
- Input device. Wired mice and keyboards generally report presses faster than Bluetooth ones, and touchscreens add their own scanning delay. Pressing a key with a short travel can be quicker than clicking a heavy mouse button.
- Your device and browser. Heavy background tasks, battery-saver modes and very old hardware can delay frames and events.
- You. Alertness, practice, focus and fatigue matter. Most people get faster over the first few rounds as they warm up.
Method and limits
When the random wait ends, the page changes the color and then records the time inside the next requestAnimationFrame callback. That callback runs at the start of the frame that actually paints the green, so the clock starts when the stimulus is drawn rather than when a timer happened to fire. Your response is timed with the input event's own high-resolution timestamp (event.timeStamp), which is set when the browser received the input — before any page code runs. Both values come from the same clock as performance.now().
The test listens for pointerdown rather than click, because a click only fires after you release the button. The random 1.5–5 second wait prevents you from predicting the change by rhythm. What a browser cannot see is the exact moment light leaves your screen or the delay inside your mouse or keyboard, so absolute numbers always include your hardware. If you switch tabs during an attempt, it is cancelled because hidden tabs stop drawing frames.
Browser and device support
| Platform | Mouse / keyboard | Touch | Notes |
|---|---|---|---|
| Chrome, Edge (Windows, macOS, Linux) | Yes | Yes | High-resolution event timestamps |
| Firefox (desktop) | Yes | Yes | Timer precision may be slightly reduced for privacy |
| Safari (macOS) | Yes | — | Works with trackpads and external mice |
| Safari / Chrome on iPhone and iPad | External keyboards | Yes | Touch scanning adds some delay |
| Chrome on Android | External keyboards | Yes | Disable battery saver for steadier timing |
Troubleshooting
- Every attempt feels slow: close other tabs and apps, plug in a laptop, use a wired mouse, and turn on a TV's game mode.
- “Too soon” keeps appearing: wait for the full color change — anticipating the signal is exactly what the random wait is designed to catch.
- The page scrolls when you press Space: click the test area once so the page has focus, then use Space.
Frequently asked questions
What is a good reaction time?
For a simple “react when the color changes” test in a browser, many people score somewhere around 200–300 ms. Because your display and input device add their own delay, the most useful comparison is against your own previous results on the same equipment.
Why is my reaction time slower on my phone?
Touchscreens scan for touches at a limited rate and phones often run in power-saving modes, both of which add delay. A desktop with a high-refresh monitor and a wired mouse usually measures faster for the same person.
Does monitor refresh rate change my result?
Yes. A higher refresh rate shows the green sooner after it is requested — at 60 Hz a frame lasts 16.7 ms, at 240 Hz only 4.2 ms — so results on fast monitors are typically a few milliseconds quicker.
Is clicking, tapping or pressing Space fastest?
It depends on your hardware. Short-travel keys and light mouse switches tend to be quick; Bluetooth devices and touchscreens are often slower. Try each a few rounds and compare the medians.
Can I improve my reaction time?
Practice, good sleep, and staying relaxed but focused all help, and most people improve over their first few rounds. Large, lasting gains are limited, but removing hardware delay (wired devices, a faster display) is an easy win.
Why don’t responses under 100 ms count?
Reacting to a visual signal in under a tenth of a second is not physiologically realistic, so such responses are almost always lucky guesses. Sports timing systems use the same 0.1-second rule to flag false starts.
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