About Reaction Time Test

ReactionTimeTestOnline.com is a free browser tool for trying a visual reaction time test and comparing your own sessions. Learn how the test works, what affects the results, and how the site handles data.

What This Tool Is For

Try a simple visual response task, see the results of five rounds, and compare your own sessions. The site is for informal practice and exploration. It is not a validated measure of cognition, athletic readiness, driving fitness, or health.

How We Measure

Our test uses performance.now() to calculate a browser time interval between the green-cue update and your response. Times are displayed in whole milliseconds. The timer’s resolution is not the same as the accuracy of the complete test.

Screen refresh, rendering, input processing, and system load affect results. The test does not detect the exact moment pixels become visible or calibrate device delays. Keep your setup consistent and interpret small differences cautiously.

Browser timing documentation: MDN — performance.now() · MDN — requestAnimationFrame()

Privacy

Test history and your challenge display name are saved in this browser using localStorage. You can remove them by clearing this site’s browser data. Challenge and result links contain encoded names and results in the URL fragment; anyone with the link can read and forward that information. Only include a name you are comfortable sharing.

The site sends page paths, referring page paths, and basic interaction events to Pageview at app.pageview.app. Events may include the challenge mode, input type, and outcome. The Pageview event payload excludes URL query strings and fragments, challenge names, and individual round times. Cloudflare hosts this site, and the live site also uses Cloudflare Web Analytics to collect visit and performance metrics. Those exclusions apply only to the Pageview event payload, not to every request handled by the hosting provider. Opening a sharing service or sharing a link or image sends the information you choose to that service or recipient.

What You Can Explore

  • Your average, best time, and variation across five rounds
  • Repeated sessions using the same screen and input method
  • Informal comparisons with friends using the same rules
  • How a browser measurement differs from a calibrated experiment