Temporal Vision

FLICKER
FUSION
TEST

A dot flickers between black and bright. Slow, you see it blink. Fast enough, it fuses into a steady glow. The speed where blinking becomes steady is your critical flicker fusion threshold — a real measure of how your eyes handle motion and refresh.

How it works

Drag the speed up

Start slow — you'll clearly see it flicker.

Stop the instant it looks steady

The moment the blinking disappears into a solid glow, lock it in.

Three rounds, averaged

We approach from slow each time and average your fusion point.

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Round 1 of 3 — raise the speed until the dot stops flickering.

6.0 Hz

Slow Fast

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Results

YOUR
FLICKER
THRESHOLD

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Note

A display can only flicker up to half its refresh rate, so this test is capped by your screen. Flicker fusion also depends on brightness, dot size, and how rested you are — it is a fun perceptual measure, not a medical test. If you reached the cap, your real threshold is simply higher than this screen can display.

About the flicker fusion test

A dot flickers between black and bright. Slow, you see it blink; fast enough, the blinking fuses into a steady glow. The frequency where flicker becomes steady is your critical flicker fusion (CFF) threshold — a genuine measure of how your visual system handles change over time.

There's a hard physical limit worth understanding: a display can only flicker up to half its refresh rate, so a 60 Hz screen caps this test around 30 Hz. We probe your display's refresh and disclose the ceiling; if you reach it, your true threshold is simply higher than the screen can show. CFF also rises with brighter light and a larger stimulus and falls when you're tired, so it's a fun perceptual measure, not a medical test.

Frequently asked questions

What is critical flicker fusion?

The frequency at which a flickering light stops looking like it's blinking and appears steady. It reflects the temporal resolution of your visual system.

What is a normal flicker fusion threshold?

Roughly 20 to 40 Hz for most people, rising with brightness and stimulus size and falling with fatigue. There's a wide normal range.

Why is the test capped by my screen?

A screen can only flicker up to half its refresh rate, so a 60 Hz display caps the test near 30 Hz. We detect your refresh and tell you the ceiling.

Does flicker fusion mean anything about my health?

It's a fun perceptual measure that shifts with lighting, stimulus size, and tiredness. It is not a medical or diagnostic test.

FLICKERFUSIONTEST

How it works

YOURFLICKERTHRESHOLD

About the flicker fusion test

Frequently asked questions

FLICKER
FUSION
TEST

YOUR
FLICKER
THRESHOLD