What is Color Blindness Simulator?

Color Blindness Simulator shows you how your images and color palettes look through the eyes of people with different types of color vision deficiency. Test for protanopia, deuteranopia, tritanopia, and achromatopsia so you can catch the colors that break for people with each one.

The simulator runs each pixel through CVD-specific colour matrices (Brettel and Machado models) to approximate how people with the eight common deficiencies perceive your image. Compare-all mode tiles every type next to the original, which is faster than toggling between them when auditing a UI mock-up or a chart.

How to use

1. Upload an image or enter colors you want to test for accessibility.
2. Pick a vision type, then drag the divider to fade between the original and the simulated view. Use the severity slider for milder anomalous cases.
3. Compare all simulation types at once and download the simulated images for documentation.

When to use

• Auditing a dashboard's status pills before a UX review.
• Checking that red/green diff highlights in a chart are still readable.
• Choosing chart palettes for a public report where readers vary.

Result

A UI designer uploads their app's dashboard screenshot and discovers that the red/green status indicators are indistinguishable under deuteranopia. They add icon shapes alongside colors to fix the issue.

FAQ

How accurate are these simulations compared to real CVD vision?

The Brettel and Machado matrices give a usable approximation, not a perfect match. Real CVD perception also depends on lighting and individual variation, so use these views to spot obvious problems, not as a medical-grade reference.

What's the difference between protanopia and protanomaly?

Protanopia is the full absence of red cones, so reds darken sharply. Protanomaly is a weakened red response — the same image looks similar but the shift is milder. Same naming pattern applies to deutera- (green) and trita- (blue).

Which CVD types are most common to design for?

Deuteranomaly affects roughly 5% of men, making it the most common red-green deficiency. Protanopia and deuteranopia together cover about 2%. Tritan and achromatopsia are rare. For broad accessibility, deutera- coverage matters most.

Can I test individual colors without uploading an image?

Yes. Switch to the Colors tab and enter any hex codes you like — each one is shown beside how all seven vision types perceive it, so you can vet a brand palette or UI token set without a screenshot. For full images, the Daltonize toggle goes a step further and recolors the picture so colorblind viewers can actually tell the shades apart.

Are my uploaded images sent to a server?

No. The image is decoded into a canvas inside your browser tab, the CVD matrix is applied locally, and the simulated version is rendered directly. Nothing leaves the page; closing the tab discards everything.

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