Honest note
How Accurate Is an Online Reaction Time Test?
Good for comparing your own tries. Not a lab measurement: your screen, input device and browser add some milliseconds.
What this site measures
The page changes the colour (or plays a sound) and notes the time with the browser’s high-resolution clock (performance.now()). When you click, it takes the time of your click event. The difference, rounded to whole milliseconds, is your result. Wait times are random between 1.5 and 5 seconds so you cannot guess the moment.
What it cannot measure
- Screen refresh. A 60 Hz screen draws a new picture every 16.7 ms, a 144 Hz screen every 6.9 ms (arithmetic: 1000 ÷ Hz). The colour change appears at the next redraw, so it can show up several milliseconds after the page decided to change it.
- Input devices. Mice, keyboards and touch screens need time to report your press. Human Benchmark gives 30 ms as a typical lag for a desktop or laptop and notes that mobile taps tend to be a bit slower.
- Sound. For the audio test, the audio system and especially wireless headphones add their own delay.
- Set-up differences. A paper on reaction time measurement (Woods et al., 2015) reports that timing delays in hardware and software can add up to 100 ms (citing Neath et al., 2011) and that results from different laboratories varied widely for that reason.
About accuracy: your browser, screen and mouse or touch screen add some milliseconds between the real moment and what the page can measure (a 60 Hz screen only redraws every 16.7 ms, and input devices add delay of their own). Your result is not a clinical measurement. It is best used to compare your own results on the same device. Details and sources
Private by design. No cookies, no account, no server. Nothing is stored unless you finish a test: then your best result is saved in this browser only (localStorage) and you can clear it above. Privacy
Frequently asked questions
Are online reaction time tests accurate?
They are consistent enough to compare your own results on one device, but they are not laboratory measurements. Delays from the screen, the browser and the input device add milliseconds, and the amount differs between set-ups.
How much delay does a computer add?
Human Benchmark says 30 ms is currently a typical lag for a desktop or laptop. A scientific paper notes that timing delays from hardware and software can increase measured reaction times by up to 100 ms (citing Neath et al., 2011), and in its own calibrated set-up the true values were 18 ms lower than the raw ones.
Does a 144 Hz monitor make my score better?
It can reduce one source of delay: the screen redraws every 6.9 ms instead of every 16.7 ms (1000 ÷ 144 and 1000 ÷ 60). Other delays remain, so we cannot promise a fixed gain.
Are phone taps different from mouse clicks?
Human Benchmark observes that mobile taps tend to be a bit slower than clicks. Keep to one device when you compare results.
Sources
- Human Benchmark: Reaction Time Statistics (median 273 ms, mean 284 ms, over 81 million recorded clicks; “30ms is currently a typical lag for a desktop/laptop”; mobile taps “tend to be a bit slower than clicks”). https://humanbenchmark.com/tests/reactiontime/statistics
- Woods DL, Wyma JM, Yund EW, Herron TJ, Reed B (2015). Factors influencing the latency of simple reaction time. Frontiers in Human Neuroscience 9:131 (Table 1, Table 2 and abstract). doi:10.3389/fnhum.2015.00131. https://pmc.ncbi.nlm.nih.gov/articles/PMC4374455/
- MDN Web Docs: Performance.now() (high-resolution time in the browser). https://developer.mozilla.org/en-US/docs/Web/API/Performance/now
- MDN Web Docs: Window.requestAnimationFrame() (callbacks run before the next repaint, usually at the display refresh rate, often 60 times per second). https://developer.mozilla.org/en-US/docs/Web/API/Window/requestAnimationFrame
Read and checked: October 10, 2026. Found a mistake? Email info@reactiontimetest.dev.