About Reaction Time Check

Reaction Time Check is a free reaction time test that reports what your hardware contributed to your score instead of quietly folding it in. It runs entirely in your browser, has no account and stores nothing on a server.

Why it exists

Every online reaction test gives you a number in milliseconds, and almost none of them mention that part of that number belongs to your screen. A display holds a change back until its next refresh, so a stimulus waits on average half a frame before your eyes can see it: 8.3 ms at 60 Hz, 3.5 ms at 144 Hz. When the whole measurement is around 250 ms, that is not a rounding error, and it is a large part of why the same person scores differently on a phone and a desktop.

This site measures your refresh rate from the browser's own frame clock and shows the raw and corrected figures side by side. It also says plainly what it cannot correct for — your panel's processing delay, your mouse or touchscreen polling, the operating system and the browser — rather than subtracting a guess and calling the result your true reaction time. How the measurement works sets out the whole chain.

Who it is for

Gamers checking whether a settings change helped, students running a class experiment, drivers finding out how far a car travels in a quarter of a second, and anyone who has just been beaten by a friend and wants a rematch. The four modes — visual, audio, choice and aim — cover the comparisons most people actually want to make.

What it is not

It is not a medical or diagnostic tool. The percentile shown with your result is modelled from published population averages for simple reaction time; it places you roughly within an age band and nothing more. It cannot assess a concussion, a neurological condition or fitness to drive, and no browser test can. If a change in your reaction or attention is worrying you, that belongs with a doctor.

Privacy

Your trial times, the age band you select and your last ten runs are stored in your own browser's local storage. They are never uploaded, there is no login, and no one — including us — can see your scores. Clearing the history in the tool or clearing site data in your browser removes them permanently.

Contact

Corrections, bug reports and questions are welcome at hello@reactiontimecheck.com. If you are reporting a scoring problem, please include your browser, your device and your display's refresh rate — that combination explains most of them.