How it works
Press Start, wait for the panel to turn green, then click or press Space as fast as you can. The delay before green is random between 1.2 and 3 seconds, so you cannot anticipate it by rhythm. Clicking before green counts as a false start and restarts the round instead of recording a time.
Five valid rounds make a result. The page shows every round, the average, and your best single round. A rating line turns the average into plain language: under 200 ms is exceptional, 200–250 ms is fast, 250–300 ms is typical for a desktop user, and above 350 ms usually means the input path is adding delay.
What the number means
Your result is the time from the visual change to the click event reaching the page. It includes your screen's refresh interval, the browser's event scheduling, and your pointing device. A wireless mouse, a trackpad, and a touchscreen produce different numbers for the same person, so compare your own runs on the same setup, not against a stranger on the internet.
The test is five rounds for a reason. Reaction time varies with attention, fatigue, caffeine, and time of day. A single round is noise. Five rounds still is not a medical measurement.
Tips for a fair run
- Use the same input device and the same screen for every run.
- Sit at a normal distance; do not chase the cursor with your eyes.
- Take the test once, not ten times. The later runs measure anticipation, not reaction.
- If you get two false starts, stop and come back later. The test rewards patience as much as speed.
What this page does not do
It does not store your results, compare you to other visitors, or send anything to a server. Nothing here is a diagnosis. If you are checking a neurological symptom, use a clinician's test, not a web page.