How ReactionF1 Measures Milliseconds
Updated 2026-08-10·By ReactionF1 Team
Event Timeline in the Game
Lights illuminate one by one. After the fifth light, a random armed delay begins. When lights extinguish, the go moment starts. Your tap, click, or keypress ends the interval. Early input during sequence or armed wait is a false start.
Why performance.now()
ReactionF1 uses the browser high-resolution timer API, performance.now(), to compute the interval between go and input. It is the standard web tool for short intervals — finer than wall-clock Date timestamps for this job.
False Starts and Clean Times
Only clean attempts produce a meaningful ms score. False starts teach patience; they are not “very fast reactions.” Compare clean medians when you track progress.
Device Lag Interaction
The number includes human response plus display, input, OS, and browser delay. Two devices can disagree by tens of milliseconds for the same person. See the device latency guide for a small same-person spot-check.
How to Cite Results
Include date, device, input, browser, clean vs false start, and that timing was browser-based. Full wording lives on the methodology page. Do not claim FIA or lab certification from a screenshot.
Ready to put it into practice? Run a clean lights-out attempt on thefree F1 start test.
Frequently Asked Questions
The lights-out transition in the browser — when the go state begins.
Your first valid input after lights out on a clean attempt.
It is high-resolution for the web, but hardware and OS still sit underneath. It is not a dedicated lab chronometer.
Early movement is not a reaction to lights out. Including it corrupts averages.
On /methodology — read that before quoting scores externally.
Explore More
Methodology & Timing
Our reaction time test uses performance.now() for millisecond-precision timing. The stimulus (lights out) and your tap are both timestamped in the browser. Your reaction time is the difference—typically within ±5 ms of true response time, depending on device and display latency.
Device latency and browser variance affect results. A 60Hz display adds up to ~16ms of delay; touch and mouse input lag also contribute. For a detailed explanation, see our device latency & reaction time guide.
Last updated: 2026-08-10 · Written by ReactionF1 Team
