Respond when the test area turns green and shows NOW. After five valid rounds, see the average and fastest round. The best individual result is stored in this browser when storage is available, not limited to today.
How to use this tool
Activate the area to begin, wait, then click, tap or press Enter or Space after the change. An early activation retries the same round. Activate between rounds to continue. If the page becomes hidden, start a new run.
What this test can and cannot show
The timer includes display, input and browser delays, so it is not a laboratory measure of biological reaction time. Compare results using the same device and input method. No medical assessment or population ranking is provided. The written cue accompanies colour for accessibility.
Updated October 1, 2026. Browser and device support varies.
Questions and troubleshooting
Is a very low score a measure of biological reaction time?
No. The interval also reflects display updates, input events and browser timing, and an anticipated click can appear unusually fast. Use the five-round average for like-for-like personal comparisons; the tool does not provide a medical assessment or population ranking.
What happens if I click before the cue?
The test marks a false start and lets you retry that round. Early activations are not included in the five valid rounds. Wait for both the green state and the written cue, then click, tap or press Enter or Space.
How this tool was checked
Automated Chromium checks on October 1, 2026 exercised keyboard activation, false-start retry and a timed valid round. Automated response times were software checks, not measured human performance.
Technical references: MDN: performance.now