How to use the color blindness simulator
- Choose a picture, such as a chart, a logo or a screenshot of a design.
- Compare the original with the simulations of protanopia, deuteranopia, tritanopia and achromatopsia.
- Look for places where two colors that are clear in the original look alike, or where meaning is lost.
- Pick a simulation and download it as a PNG if you want to share it.
The model used
The simulation applies the dichromacy matrices at severity 1.0 from Machado, Oliveira and Fernandes (2009), in the paper A Physiologically-based Model for Simulation of Color Vision Deficiency, IEEE Transactions on Visualization and Computer Graphics, volume 15, number 6. The matrices were read from the authors' page, fetched on 2026-10-13. Each color is converted from sRGB to linear light, multiplied by the matrix for the kind you choose, clipped to the displayable range and converted back. Achromatopsia is shown as the luminance of each pixel, using the Rec. 709 weights.
The three matrices have rows that add up to 1, so white, black and grays are unchanged. Red under protanopia becomes a dark olive, and a bright green becomes a yellowish color. These are examples of what the matrices do, and they are not a promise about how any one person sees.
It is an approximation
Real color vision varies from person to person, and most people with a color vision difference have a milder form than the full dichromacy shown here. Screens, brightness and the surroundings also change what anyone sees. A simulation is a quick way to spot designs that depend on color alone, such as a chart with red and green lines. It cannot tell you how a particular person will experience the picture, so test with people when it matters.
Good designs add a second cue, such as labels, patterns, shapes or position. For numbers on contrast, use the color contrast checker, and to build palettes try the color palette generator and the color picker.
Large pictures and privacy
Pictures bigger than 1,600 pixels on the long side are reduced so the page stays quick, and the page shows the size it used. The picture is read in your browser and nothing is uploaded.
Assumptions and limits
- Matrices are the Machado et al. (2009) severity 1.0 dichromacy matrices, applied in linear RGB.
- Achromatopsia is shown as grayscale from the Rec. 709 luminance.
- Milder forms of color vision difference are not shown.
- The result is an approximation and screens differ.
Frequently asked questions
How do I see my design as a color blind person would?
Choose a picture of your design. The page shows it under protanopia, deuteranopia, tritanopia and achromatopsia next to the original.
Is the simulation exact?
No. It is an approximation based on a published model, and real vision varies. Use it to find problems, then confirm with people.
What can I do if my chart fails the check?
Add labels, patterns or different shapes so color is not the only cue, and pick colors that differ in brightness as well as hue.
What do the four types mean?
Protanopia and deuteranopia affect reds and greens, tritanopia affects blues and yellows, and achromatopsia means no color vision.
Is my picture uploaded?
No. The picture is processed in your browser.