What it does
Useful, focused capabilities
- Visual and four-arrow choice modes
- 3, 5, or 10 trial sessions
- Randomized delay and false-start handling
- Median, average, best, and variability
- No medical claims or fabricated percentiles
Skill & performance · browser-local
Reaction time test
Test reaction time locally with visual and choice modes, false-start handling, session median, variability, and private on-device history.
Work happens in the current browser. The route does not require an account or a server-side processing job.
Interactive browser workspace
Reaction time test
The live tool is loaded in this browser only. This route does not need camera, microphone, or screen-capture permission for its main task.
Load the interactive workspace →Browser compatibility
Requirements and honest fallbacks
JavaScript and a modern browser; keep the tab visible and use pointer or keyboard input for meaningful timing.
- JavaScript
- pointer or keyboard input
- Local storage
Questions people ask
Clear answers and limits
Is this a medical reaction-time test?
No. It is a browser interaction test and cannot diagnose a neurological, attention, vision, or motor condition.
Why does the page cancel a hidden-tab trial?
Browsers can delay timers and rendering in hidden tabs. Cancelling protects the result from a known source of distortion.
Why use the median?
A median is less sensitive than an average to one unusually slow interruption or one unusually fast anticipated response.
What counts as a false start?
Any response before the signal, plus implausibly early responses below the conservative browser threshold, restarts the trial without saving a time.
Can I improve reaction time with this tool?
Repeated practice may improve familiarity with this exact task. The tool does not promise transfer to driving, sport, gaming, or clinical performance.
What this tool checks
Run a local reaction-time exercise with visual or four-choice cues, randomized delays, false-start handling, and a session median. The report can include average, best, variability, and trial outcomes; local history is optional. Keep the tab visible because hidden-tab throttling cancels affected trials. Compare sessions only under similar device, display, input, and browser conditions. This is a browser interaction measurement for practice, not a medical, driving, sport, or clinical assessment.
What to choose and what you get
What to choose
- pointer or keyboard responses to visible reaction cues
Result
- an on-page reaction-time result and a downloadable PNG result card
Supported use
- Visual and four-choice modes with 3-, 5-, or 10-trial sessions.
- Randomized delay, false-start handling, median, average, best, and variability reporting.
Before you start
- It does not diagnose a neurological, attention, vision, or motor condition.
Supported formats
- Accepted formats: keyboard, pointer, timing, browser state.
- Output formats: HTML report, PNG.
Browser support and permissions
- Modern browser with JavaScript; timing, scheduling, clipboard, and device behavior vary by browser.
- No camera, microphone, or screen permission is needed.
Choose the right settings
- Choose this route for visual or choice reaction practice.
- Use /aim-trainer for target acquisition and tracking.
- Use /stopwatch-timer for laps or a countdown rather than cue response.
Worked example
A visual reaction session needs a median across several trials while false starts and hidden-tab trials remain visible.
Starting facts
- Display, input device and browser scheduling add latency.
- One trial is not a stable personal measurement.
Observed operation: Wait for each visible cue, respond with the chosen input and calculate median, average, variability and false starts locally.
Review the result: Use the session distribution rather than one fastest trial and compare only matching foreground device conditions.
Boundary: The browser result is not a medical assessment, calibrated latency measurement or proof of neurological performance.
Choose another tool when
- The result is not a medical, driving, sport, clinical, or identity-verified assessment.
If it does not work
- A hidden tab can cancel a trial because delayed timers and rendering would distort the interval.
- Responses before the cue or below the conservative early-response threshold are treated as false starts.
- A blocked storage API prevents local history from being retained.
Things to know
- Measured intervals depend on display refresh, input latency, browser scheduling, device, and visible-tab state.
Privacy boundary
Browser interaction and local results stay in the current browser session and are not sent to an Aftermath processing service. How local processing is verified.
What this tool verifies
Reports reaction-time trials, false starts, median, average, best, and variability for the selected browser session.
Check before sharing
The result describes responses to this page's cues under its device and browser conditions; it is not a medical or real-world performance assessment.