What this test measures
This is a simple visual reaction time test: one signal, one response, no decision to make. The panel turns dark blue and says “Wait…”. After a random pause of 1.5 to 4.5 seconds it switches to yellow-green with the word “GO!”, and the clock stops the instant you press. Because the pause is random you cannot count your way to the change; you have to see it.
A round is five trials by default (ten if you want a steadier number). Two kinds of press are thrown out and repeated. A press before the change is a false start. A press less than 100 ms after it is counted as a guess too, because no one can see a change, recognise it and move a finger that quickly. A trial slower than two seconds is skipped as well, since it almost always means you looked away. What remains is summarised four ways: the median, the mean, your fastest trial, and the spread (standard deviation), which tells you how consistent you were.
How your result is timed
Most online tests start the clock when they ask the browser to change the colour, but the new colour only reaches your eyes at the screen’s next refresh. Here the colour change is made at the start of a frame and the clock starts with the following frame, which is when the changed picture is actually on the glass. The stop time comes from the moment your mouse button, finger or key went down — not from the later “click” that browsers fire when you let go.
Both timestamps come from the browser’s high-resolution clock. MDN documents its resolution as 100 microseconds on normal pages, far finer than anything a reaction test needs. What still lands in your score is the hardware: how long your input device takes to report, and how long the screen takes to draw. That is why the “Your setup” box measures your refresh rate while you play.
What is a normal reaction time?
The best modern reference is a 2015 study by Woods and colleagues that built a calibrated test and measured 1,469 adults aged 18 to 65. Their average was 231 ms, and 213 ms once the delay of their own display and mouse (17.8 ms on average) was taken out. Older textbook figures for college-age people are around 190 ms for a light. Sound is faster than light for the same task: the same textbook figure for a sound is about 160 ms.
| Reference | Typical value | Who and how |
|---|---|---|
| Lab, equipment delay removed | 213 ms | 1,469 adults aged 18–65, calibrated rig (Woods 2015) |
| Lab, including its own equipment | 231 ms | same study, raw average |
| Textbook figure, light | ≈ 190 ms | college-age adults, cited by Jain 2015 |
| Textbook figure, sound | ≈ 160 ms | same source |
| Change with age | +0.55 ms per year | Woods 2015, mostly slower movement rather than slower seeing |
The Woods paper notes that ordinary computer hardware can add far more delay than a calibrated rig, so a median of 250–300 ms here is perfectly ordinary. The numbers are a rough frame, not a grade.
What changes your reaction time
- Your equipment. At 60 Hz a frame lasts 16.7 ms; at 144 Hz, 6.9 ms. A mouse polling at 125 Hz reports every 8 ms, one at 1000 Hz every 1 ms. Touch screens and TV picture processing can add more on top.
- Sleep. Lack of sleep slows responses overall and causes long lapses — the review by Lim and Dinges describes both effects on a standard vigilance reaction test.
- Caffeine. A review of the research found that low to moderate doses improve alertness, attention and reaction time.
- Fatigue within a session. In the Woods study the average drifted from 228 ms in the first block to 237 ms in the last. Long sessions are not better sessions.
- Age. Simple reaction time slows by roughly half a millisecond a year in adults, and the same study found the slowing sits mainly in the movement, not in noticing the signal.
- The wait before the signal. Woods and colleagues found reaction times were longer when the gap before the signal was shorter. The random 1.5–4.5 second wait here keeps you from timing the change.
How to get a faster, steadier score
- Do one warm-up round and ignore it, so the timing feels familiar. The lab study above also gave everyone practice trials before measuring.
- Rest a finger lightly on the mouse button, key or screen so the press is a small movement, not a reach.
- Look at the middle of the panel and relax your eyes; you do not need to stare.
- Close busy tabs and plug in your laptop — power saving can lower the frame rate.
- Use the fastest display mode you have: “game mode” on TVs, the highest refresh rate on monitors.
- Track the median over several days on the same device. A smaller spread is progress too.
Built for keyboards, touch and colour-blind players
The usual red-to-green reaction test relies on the colour pair that red-green colour blindness confuses, and the US National Eye Institute says about 1 in 12 men have some form of colour vision deficiency. Here the change is from a dark, dotted blue to a bright, plain yellow-green, the text changes from “Wait…” to “GO!”, and the icon changes shape. The panel changes colour once per trial and nothing on the page flashes, which keeps well within the W3C guideline of no more than three flashes in any second.
For fun and practice only. This test does not diagnose anything, and a slower score on one day says nothing about your health.