How You See

Color blindness simulator

Choose a type and severity. The picture is recomputed with a published physiological model.

Simulations follow Machado, Oliveira and Fernandes (2009). They show an average of how colors collapse for each type; they cannot show what any one person experiences, and this is not a test for color blindness.

How the simulation works

The tool uses the model of Machado, Oliveira and Fernandes (2009), which is built on the stage theory of human color vision and handles anomalous trichromacy and dichromacy in one framework[1]. For each type (protan, deutan, tritan) and severity from 0 to 1 in steps of 0.1, the authors published a 3×3 matrix that acts on linear RGB values; this tool interpolates between neighboring severities. Each pixel's sRGB values are first converted to linear light and afterwards converted back, using the transfer function in the CSS Color 4 specification[2]. Severity 1 approximates the missing cone (dichromacy); lower severities approximate a cone that is present but works abnormally.

TypeCone affectedFull form / milder form
ProtanL (long-wavelength)protanopia / protanomaly
DeutanM (middle-wavelength)deuteranopia / deuteranomaly
TritanS (short-wavelength)tritanopia / tritanomaly

Red–green deficiency (protan and deutan) is by far the most common; deuteranomaly is the most common single type[3]. Large surveys find red–green deficiency in about 8% of men and 0.4% of women of European descent[4].

Using it

The most practical use is checking designs. Load a chart, map or slide with Your own image: it is processed in your browser and never uploaded. If two categories you need to tell apart become the same in the simulated picture, add a second cue such as a label, a shape, a pattern or a difference in lightness.

The limits matter. A simulation shows an average loss for a type, not any one person's experience, and an uncalibrated screen changes the input colors.

This is not a color blindness test and not medical advice. Nothing here can tell whether you are color blind. Testing is done with standardized plates or instruments under controlled lighting; if you have questions about your color vision, see an optometrist or ophthalmologist.

Sources

  1. G. M. Machado, M. M. Oliveira and L. A. F. Fernandes (2009). A physiologically-based model for simulation of color vision deficiency. IEEE Transactions on Visualization and Computer Graphics 15(6), 1291–1298. doi:10.1109/TVCG.2009.113. paper
  2. T. Atkins Jr., C. Lilley and L. Verou (editors) (2025). CSS Color Module Level 4: §18 Sample code for color conversions (sRGB transfer function; XYZ D65 to linear sRGB matrix). World Wide Web Consortium (W3C). standard
  3. National Eye Institute (2023). Types of color vision deficiency. National Institutes of Health. institutional
  4. J. Birch (2012). Worldwide prevalence of red-green color deficiency. Journal of the Optical Society of America A 29(3), 313–320. doi:10.1364/JOSAA.29.000313. paper