Why this exists
A reaction time test looks like the simplest thing on the web: wait for a color, click, read a number. The trouble is in details nobody sees. A test can time your click when the button is released rather than when it goes down, or start its clock before the color is actually on screen, and either one adds time that is not your reaction. A result that says nothing about your screen’s refresh rate leaves you guessing how much of the number the screen added. If a page is going to hand you a number in milliseconds, the milliseconds should be the part that is engineered, so this test handles all three, as described below.
How this one measures instead
The press is timed on pointerdown: the instant the mouse button goes down or your finger touches the screen, not the moment you let go. Timing the release would add however long your finger rests on the button to every result.
The clock starts on the frame that draws the green, not when the code asks for the color to change. A browser only puts a new color on screen when it draws its next frame, so a clock started any earlier includes a wait that has nothing to do with you.
And the test tells you what your screen’s refresh rate adds. A 60 Hz screen draws a new frame about every 16.7 milliseconds, a 120 Hz screen about every 8.3, and a 144 Hz screen about every 6.9. That difference is real, it sits inside every result, and it is not your reflexes. Knowing it lets you compare a laptop result with a gaming monitor result without fooling yourself.
What it cannot measure
Some delay happens where no web page can see it. A mouse or keyboard takes time to notice a press and report it to the computer, and a monitor takes time to process a frame and change its pixels. Both add to every result, both vary from one device to the next, and the browser receives no signal of either, so neither can be subtracted. That is why the same person can score differently at two desks, and why a result here is best compared with your own earlier results on the same setup.
It is also not a scientific instrument or a medical test. It cannot diagnose anything, and it cannot tell you whether you are fit to drive, work or play. It is a fun measurement that tries to be honest about what is inside the number.
What was left out on purpose
No accounts and no sign-up, because a reaction test does not need to know who you are. No leaderboard, because your results never leave your device: every click, tap and key press in the test is timed and scored in your browser. No contact form either — a form is a data-collection point, and we would rather publish an email address. The one thing the test remembers is your best average in each mode, kept in your browser so it is still there next time. Clear your browser data and it is gone, because we never had a copy. The details are in the privacy policy.
Who runs it
A small independent project, not a company. If something is broken, a number looks wrong, or a claim on this page does not hold up on your device, email hello@myreactiontimetest.com — it reaches a person.