Ishihara Color Blind Test — Classic Digit Plates, Free Online

The Ishihara color blind test is the format everyone pictures: a circle of mottled dots with a number printed inside in a second color family. This Ishihara color blind test runs nine such digit plates, generated by a seeded open-source algorithm so every visitor sees exactly the same test — plate for plate, dot for dot. It is the classic red-green screening experience, and the whole color blind test takes about ninety seconds.

In 1917, Japanese ophthalmologist Shinobu Ishihara published a set of pseudoisochromatic plates to screen soldiers for red-green deficiencies. The design principle still defines the genre: scatter dots of randomized size and lightness across two color families, draw the figure with one family and the background with the other, and rely on the fact that deficient red-green perception collapses the two families into near-identical appearance. An Ishihara color blind test built on this principle behaves like the original — but the plates in this Ishihara color blind test are NOT scans or copies of the copyrighted printed booklet.

Our plates come from the MIT-licensed `ishihara` Python generator by Vincent Gonzalez: each digit plate is grown from a fixed seed, which fixes the dot layout, the color palette and the answer. The same seed always yields the same plate, so the test is reproducible in a way random per-visit generators are not — you can even verify the checksums of every SVG on our licenses page.

• 1One control plate printed in brightness-contrast colors opens the test — if you cannot read it, your screen or settings make the session uninterpretable.
• 2Eight red-green digit plates follow, one at a time; type the number you actually see, or press "I can't see it".
• 3The result page reports how many figures you recognized — red-green designs as one group — with no diagnosis, subtype or percentage.
• 4Retake as often as you like; the plates are identical each time, so repeated exposure can train your answers — worth knowing before your second run.

Deliberately, this Ishihara color blind test never claims clinical accuracy. The original 24- and 38-plate books are validated instruments administered under standardized daylight illumination. A browser plate set on an uncontrolled screen is a screening experience — strong signal, no verdict. The U.S. National Eye Institute describes pseudoisochromatic plates as one screening method among several that clinicians combine (NEI, testing color vision).

Digits that transform under red-green deficiency

Classic Ishihara color blind test logic includes transformation plates: a person with typical vision reads 74 where a red-green deficient reader reads 21, or reads 3 where the deficient reader sees 8. Our generator produces single-axis red-green plates rather than deliberate transformation pairs, so the meaningful signal in this Ishihara color blind test is figures that blur, vanish or get misread — and the control plate that anchors the session.

What a misread on the Ishihara color blind test means

One misread plate means little — screen glare and stale panels cause single misses constantly. A run where most red-green plates of the Ishihara color blind test blur is a reasonable prompt to book a clinical exam, especially before occupational screening for aviation, railway, electrical or maritime roles where formal color standards apply.

Why blue-yellow plates are not in this set

The Ishihara color blind test is a red-green instrument by design; its confusion palettes say nothing reliable about tritan (blue-yellow) vision. We keep the axes separate on principle. For that axis use the tritan color blindness test.

• Disable night shift, blue-light filters and system color filters before the Ishihara color blind test — warm tints mimic deficiency.
• Clean the screen, use moderate brightness in normal indoor light, and avoid direct reflections.
• Wear your usual corrective lenses, but remove tinted or anti-blue-light glasses.
• Answer the Ishihara color blind test with your first honest impression; guessing sharp digits defeats the measurement.

Related experiences: the online Ishihara test variant of this same engine, our full 14-plate color blind test, and the color blind simulator for seeing any photograph under simulated color vision.