Color Blindness Simulator

The common ones are red-green deficiencies: protanopia (missing red cones) and deuteranopia (missing green cones), which together affect roughly 8% of men and 0.5% of women. Tritanopia (missing blue cones) is rare, and achromatopsia (little or no color perception) is very rare. This tool simulates all four at full severity; the achromatopsia panel is a luminance-preserving grayscale and doesn't model the reduced acuity or light sensitivity that often accompany it.

It uses the Machado, Oliveira & Fernandes (2009) model — a physiologically-based method, and the same model Chrome DevTools uses for its built-in color-vision emulation. We apply the transform in linear light (the sRGB color is decoded to linear, transformed, then re-encoded), which the more rigorous references treat as more accurate across the full brightness range. The original paper applied the matrices in gamma-encoded sRGB and found the difference small, so you may see minor variation between tools — it's a simulation, not a medical diagnosis.

Protanopia and deuteranopia both impair the red-green axis, so colors that differ mainly along it (a red and a green of similar lightness) collapse toward the same muddy yellow-brown. That's exactly why color alone is an unreliable way to convey meaning — pair it with text, icons, or patterns.

No. The simulation runs entirely in your browser with a small matrix multiply. The color you're testing is encoded in the URL (so you can share a result), but nothing is uploaded.

Don't rely on hue alone to distinguish important states — vary lightness too, and add a non-color cue. Use the contrast checker to keep text legible, and check that semantically-different colors stay distinguishable across the columns here (especially protanopia and deuteranopia).