Reaction Time Test

How to use

1. 1Pick 3, 5, or 10 trials per session. Five is enough for a stable median; ten is better if you want to compare days.
2. 2Click the panel, or press space, to begin. The panel turns red.
3. 3Wait. The red phase lasts a random delay between 1.5 and 5 seconds, so you cannot predict when it ends.
4. 4When the panel turns green, click or press space as fast as you can. The reaction time in milliseconds is recorded.
5. 5If you click during the red phase it counts as a false start and the trial is retried automatically. False starts are listed in the trial log but do not enter the average.
6. 6After the last trial, the summary panel shows best, average, median, slowest, and standard deviation, plus the benchmark band your average falls into.
7. 7Use Copy report to grab a plain-text block of every trial and the session summary, or click Run another session to repeat the test.

About this tool

Reaction Time Test measures simple visual reaction time, the millisecond delay between an unpredictable green-light stimulus and your first click, tap, or space press. Each session runs a chosen number of trials (3, 5, or 10). Inside a trial the panel turns red for a random delay of 1.5 to 5 seconds, then turns green; your first input ends the trial and the elapsed time in milliseconds is recorded. Clicking during the red phase is recorded as a false start so you cannot game the test by spamming the panel, and the trial automatically retries after a short pause. If the panel stays green for more than 8 seconds without an input, the trial is recorded as a timeout. The timer uses the high-resolution monotonic clock the browser exposes through performance.now and the DOMHighResTimeStamp on each click event, and anchors the start moment inside a requestAnimationFrame callback so the recorded zero is the same frame your eye actually sees the colour change, removing one frame of drift that a naive implementation would introduce. After every session the tool shows the best single trial, the arithmetic mean, the median (which is more honest than the mean when one trial is a slow outlier), the slowest valid trial, and the population standard deviation across trials so you can tell whether you were consistent or all over the place. Trials that were false starts or timeouts are counted separately and do not pollute the average. The benchmark band that follows your average is a rough guide to the published consensus for simple visual reaction in healthy adults, where around 250 milliseconds is typical, under 200 milliseconds is fast, and anything under 150 milliseconds usually means anticipation rather than reaction. Real reaction varies with sleep, fatigue, caffeine, age, input device, and mouse polling rate, so the median of 10 trials is a more useful number than a one-off lucky best. The whole test runs entirely in your browser. No timing data, click history, or device information is sent anywhere. Use it before a race, before a gaming session, after a coffee, after a poor night of sleep, or simply to compare with the published reference values, and use Copy report to share your trial log as a clean text block.

Free to use. Works in your browser. No signup, no login.