⏱Reaction time test: how many milliseconds are actually yours?

It is slightly better than average for an adult. The largest published sample, 1,469 people aged 18 to 65, put the mean simple visual reaction time at 231 ms, and that was on laboratory equipment with 18 ms of hardware delay already removed. On a browser, with a consumer screen and mouse in the chain, a genuine 200 ms is a good result. Below 150 ms is faster than the visual system normally manages and usually means an anticipated click.

Three reasons, and all of them are worth 10 to 30 ms. Sites start the clock at different points, some when the colour change is requested and some when the frame carrying it is actually rendered. Stimuli differ: a colour change is spotted faster than a shape appearing. And browsers coarsen their timers against fingerprinting, with Firefox rounding event timestamps to 2 ms by default and to 100 ms if resistFingerprinting is switched on.

Yes, and predictably. A display shows one frame at a time, so a target that becomes visible has waited on average half a frame to be lit: 8.3 ms at 60 Hz, 2.1 ms at 240 Hz. Add the panel’s own response time on top. The same person tested on a 60 Hz laptop and a 240 Hz monitor will usually be 5 to 10 ms apart before the mouse has contributed anything.

It matters, by a smaller amount than the screen. A 125 Hz mouse holds a press for up to 8 ms before reporting it, so it costs 4 ms on average; a 1000 Hz mouse averages 0.5 ms. Modern wireless receivers add roughly a millisecond and are no longer the weak link. Across the whole input path, expect 2 to 10 ms — real, but smaller than the difference between two people on the same equipment.

Because attention lapses are not symmetrical: you can be 40 ms slower than usual but almost never 40 ms faster. Over five rounds a single distracted attempt at 500 ms adds 50 ms to the mean while the median does not move at all. That is why the best round is the number people quote and the average is the number that describes them.

It does, and more slowly than the internet suggests. The same 1,469 person study found simple reaction time rising 0.55 ms per year of age, which is about 26 ms across the whole 18 to 65 span. That is roughly four times the 6 ms you would gain by moving from a 60 Hz screen to a 240 Hz one — the ageing effect is real, but it is the same order of magnitude as the hardware you are testing on.