ChromaCheck generates genuine Ishihara-style test plates in your browser, calibrated along real dichromat confusion lines — then tells you exactly which color pairs your eyes struggled with.
The number hides in red-orange dots among yellow-greens whose brightness matches exactly — so it vanishes when the red–green cone axis collapses, and survives when it doesn't. Every plate in the test is built this way, from first-principles cone fundamentals rather than scanned images.
Ishihara-style · 14 plates · ~3 min
Vanishing plates, sensitive plates, protan/deutan/tritan probes and one transformation plate. The report details every color pair you could not separate, suggests the deficiency type and severity, and simulates how each dichromat would see the same plates.
7 colors × 3 shades · 21 rounds · ~2 min
A dedicated rainbow-naming test: Violet, Indigo, Blue, Green, Yellow, Orange and Red — each in vivid, soft and deep shades. Your errors are matched against how protanopes, deuteranopes and tritanopes would name the same swatches.
Your retina has three cone classes — L (long/red), M (medium/green) and S (short/blue). Roughly 1 in 12 men and 1 in 200 women inherit a shifted or missing cone, collapsing part of the normal 3-D color space into 2-D. Reds, greens and browns merge for protan/deutan types; blues and greens (or yellows and violets) merge for the much rarer tritan type.
Classic Ishihara plates hide a number in dots whose colors sit on a dichromat's confusion line. This app computes those lines from cone fundamentals: for example, the rose-red and green dots of the deutan-probe produce literally identical L- and S-cone signals for a deuteranope, so the number disappears — while a protanope, who keeps a different pair of cones, still reads it.
Naming colors is a different task than detecting faint numbers. The spectrum test maps your color categories directly: which shades you merge, in which direction, and how your error pattern correlates with protanope, deuteranope and tritanope naming models. Together the two tests cross-check each other.
Screens are not calibrated monitors, and this is not a diagnostic instrument. Mild anomalous trichromacy is genuinely hard to detect on any consumer display. Treat results as a screening signal — and see an eye-care professional for anything that matters.
Medical disclaimer
ChromaCheck is an educational screening tool. It cannot diagnose color vision deficiency and must not be used for employment, licensing or medical decisions. Consult a qualified eye-care professional for a definitive assessment.