Reaction Time Test — Measure in ms
A click-on-green reaction time test with five-try average and median
Runs in your browser · nothing is uploaded
Do not press while the screen is red. The moment it turns green, press with the mouse, a tap or the Space or Enter key as fast as you can. Repeat five times to get an average.
The time shown also contains the monitor refresh interval and the delay of your input device and browser. It is meaningful for comparing runs on the same device and hard to compare directly with other people.
Your times are never sent to a server. Only the best and recent 5-try averages stay in this browser so you can compare next time (Clear records removes them).
What it is
The Reaction Time Test measures how long you take to respond when a block of color changes from red to green, in milliseconds. People use it to check their form before gaming, to see whether a new mouse or monitor feels different in numbers, or to find out how sleep or caffeine affects their response. It runs five tries and shows the average, the median and your best time, so one lucky or unlucky try does not decide the result.
How to use
- Click, tap or press Space on the blue area to begin.
- While the area is red, wait. It turns green after a random delay between 2 and 5 seconds.
- The instant it turns green, respond as fast as you can. Your time in ms appears on the area.
- Press the area again to move on to the next try. There are five in total.
- After the fifth try you see the average, median, best and slowest times plus the list of attempts. Pressing the area again after that does nothing, so a stray tap cannot wipe your results. Use the Start over button below to go again.
- If you press too early, that try is not recorded. Press again to repeat the same try.
How it works
- When the clock starts: the tool notes the time just before green is painted, using the browser’s high-resolution timer (performance.now). It stops when your input event is handled and rounds the difference to whole milliseconds. Mouse and touch count at pointer down and the keyboard at key down.
- Waiting time: a delay between 2,000 and 5,000 ms is picked with the browser’s secure random generator, so you cannot predict the moment.
- Early presses: a press before green is not scored.
- Average and median: the average is the sum of five tries divided by five, rounded. The median is the middle of the sorted list.
- Built-in delays: the time includes the monitor’s refresh interval (about 16.7 ms at 60 Hz), the delay of the input device and operating system, and browser processing. That makes the figure larger than your pure nervous system reaction.
Examples
| Try | Time |
|---|---|
| 1 | 248 ms |
| 2 | 231 ms |
| 3 | 305 ms |
| 4 | 240 ms |
| 5 | 236 ms |
For these times the average is 252 ms (1,260 ms divided by five), the median is 240 ms and the best is 231 ms. One slow outlier like try 3 raises the average but hardly moves the median.
FAQ
What happens if I press too early?
Pressing while the screen is red does not count. A yellow notice appears, and one more press starts the same try again with a new wait. The screen turns green after a random delay between 2 and 5 seconds, so guessing the timing does not work.
Why show the median as well as the average?
If your mind wanders on one of the five tries and you respond slowly, the average jumps. The median is the middle value when your times are sorted, so a single slow try barely moves it. A big gap between the two means your times were uneven.
Does my monitor or mouse change the result?
Yes. The monitor refresh rate, the response delay of your input device, wireless connections and the browser's own processing are all included in the time. Use the test to compare runs on the same device, and treat comparisons with other devices or other people as rough at best.
Can I use the keyboard?
Yes. When the colored area has focus, Space or Enter acts like a click. For mouse and touch, the time is taken when the button goes down, not when it comes back up.
Are my times saved or sent anywhere?
They are never sent to a server; timing and calculation happen inside your browser. So you can track your form or practice, the best 5-try average and the last five averages stay in this browser, and Clear records deletes them at any time.
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