Home Reaction time
Reaction time
Press start and wait. A signal at 1,000.0 and a click at 1,250.4 read 250 ms. A click before the signal stops.
Why this exists
Reaction time is the gap from the green signal to the click, rounded to whole milliseconds.
Each round picks a fresh wait from 1,000 through 4,000, so the signal time cannot be memorized.
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01How to use it
Start changes the panel to wait.
A click after the panel turns green and says now shows the milliseconds.
Copy puts one line such as 250 ms on the clipboard.
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02What you get
1,000.0 and 1,250.4 are 250 ms.
A unit of 0 waits 1,000 ms.
A unit just under 1 waits 4,000 ms.
Entered1,000.0 to 1,250.4
1,000.0 → 1,250.4 250 ms unit 0 1,000 ms just under 1 4,000 ms gap 10,000 10,000 ms -
03Worth knowing
A click before the signal is early.
10,000 ms stays, and a larger rounded gap is late.
This page does not read the stopwatch laps.
Closing the tab clears the time. Nothing is sent to a server.
Questions
- QWhat if I click at 1,250.4?
- AIf the signal was at 1,000.0, it is 250 ms.
- QWhat if I click early?
- AIt is early. The time stays hidden.
- QWhat about 10,000 ms?
- A10,000 ms remains a result, and anything above stops.
- QIs this a clinic test?
- ANo. It is only a click gap in this browser, and nothing is sent to a server.
How this page works it out
This page times the click after the green signal. The wait after start is a whole number of milliseconds from 1,000 through 4,000. A unit of 0 waits 1,000 ms, and a unit just under 1 waits 4,000 ms. A signal at 1,000.0 and a click at 1,250.4 differ by 250.4, which rounds to 250 ms.
A click before the signal is early. That click is not timed. A rounded gap past 10,000 ms is late and stops. 10,000 ms still counts. The clock is performance.now in this browser. It does not read the lap list on the stopwatch page.
The time is measured only on this screen. It is not a clinic record and it is not a medical exam. Closing the tab clears the time. Nothing is sent to a server.