Reaction time test
Wait for the hidden signal, then tap or press Space the instant the panel says NOW. Five randomized trials, with your best kept on this device.
Complete five trials using one input type. The median is the main result because one distraction changes it less than an average. False starts are never counted.
Reaction test ready.
How the reaction time test works
- Start with a keyboard, mouse, touchscreen, or pen. That exact input type is used for all five trials.
- Wait through a different hidden delay on every trial. Pressing early creates a false start and is not counted.
- Respond when NOW appears. Your five results are summarized with the median as the main score.
What the millisecond result measures
The test uses your browser's monotonic performance clock and rounds the result to the nearest millisecond. It measures the whole path from the visual signal through your display, attention, input hardware, operating system, and browser. It is useful for comparing your own attempts on the same setup, but it is not laboratory equipment.
Nanoseconds would be misleading here. A single display refresh already takes several milliseconds, and keyboards, mice, touchscreens, and browsers each add their own delay.
Where your results are kept
Completed sessions are saved in this browser on this device only. Nothing is uploaded, there is no account, and clearing your browser data removes them. The newest 25 sessions are kept, plus your fastest single reaction, which is stored separately so trimming the list can never quietly lose a record. Clear history removes both immediately.
The saved summary reports medians rather than averages. One distracted trial moves an average far more than it moves a median, so a median is the more honest description of how you actually reacted across a session. If your browser is in private mode or its storage is full, the test still runs and a short note says nothing was saved.
How to get more consistent results
- Keep this tab visible and avoid switching windows during a trial.
- Use one input method for the full session instead of mixing touch, mouse, and keyboard.
- Run several sessions on the same device and compare medians rather than one unusually fast attempt.
- Close heavy background work if the page or device is visibly stuttering.
Common questions
Why does the test use milliseconds instead of nanoseconds?
Human visual reactions and consumer input devices operate on a millisecond scale. Reporting nanoseconds would imply precision the display, browser, and hardware do not provide.
Does monitor refresh rate affect reaction time?
Yes. The signal can only become visible on a display refresh, while input polling and system scheduling add more delay. Compare results on the same setup for the fairest trend.
Can this diagnose a medical or driving issue?
No. This is an informal browser activity, not a medical, occupational, or driving-fitness test. Contact a qualified professional when an official assessment matters.