Color blindness simulator
See how an image, website or color palette looks to people with protanopia, deuteranopia, tritanopia or achromatopsia.
How to useSimulate color blindness.
Available in: 
Color blindness simulator: what it is for
Upload an image, such as a screenshot of your site, a chart or a logo, or type a color palette, and see side by side how it looks with each type of color blindness. The simulation uses the Machado, Oliveira and Fernandes matrices, with an intensity control for milder cases (anomalies).
Everything runs in your browser: nothing you paste or open is sent to a server.
How to use
- Choose an image or type the colors.
- Compare the five views.
- Adjust the intensity if you like.
When to use it
- Test the accessibility of sites and charts.
- Pick palettes that work for everyone.
- Understand how a color-blind person sees.
Frequently asked questions
How many people are color blind?
About 8% of men and 0.5% of women have some form of color blindness. The most common is difficulty with green and red (deuteranomaly and protanomaly).
How is the simulation done?
Each pixel goes through a color matrix based on the Machado, Oliveira and Fernandes (2009) model, which reproduces the loss of one of the retina's three cone types. The intensity slider goes from normal vision to complete loss of the cone.
How do I use this in design?
Check that charts, buttons and alerts stay understandable in all four simulations. If something relies only on color, add icons, text, patterns or more light-dark contrast.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 are free.