Color blindness simulator
See an image the way color-blind people do: protanopia, deuteranopia, tritanopia, achromatopsia and milder forms. Check charts, websites and posters.
- Free
- No sign-up
- No file uploaded
- Windows, Mac, Android, iPhone
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About this tool
Check that a chart, web page, poster or game stays readable for color-blind people. The tool simulates the 8 forms of color blindness, next to the original or all at once, using a recognized scientific model. The computation happens on your device.
When to use it
Check the accessibility of a website or app
Take a screenshot of your interface and paste it: you immediately spot a red error button that no longer stands out from a green one, or a link that disappears into the text.
Review a chart or map before publishing
Line charts, pie charts and heat maps often rely on red and green. The overview shows at a glance whether the series remain distinguishable.
Understand what a loved one sees
Parents, teachers or colleagues can see concretely why a child mixes up certain crayons or why a colleague asks for labels.
How to use
- Choose an image or paste a screenshot (Ctrl+V).
- Choose a type of color blindness, or show all 8 types at once.
- Compare with normal vision and spot the colors that get confused.
- Save the simulations to share them with your team.
How it works
Each pixel's colors are converted to linear RGB, the space of physical light, then transformed by the Machado (2009) matrix for the type of color blindness: the eye's three types of cones are modeled, and the absence of one of them shifts the perceived colors.
The milder forms (anomalies) are obtained by blending normal vision with the full form according to the chosen strength. Achromatopsia is simulated with perceived luminance, with no color at all. The result is converted back to sRGB for display and saved as a lossless PNG.
Tips for best results
- Test deuteranomaly and protanopia first: they are the most common forms.
- Always pair color with another cue: text, icon, pattern or shape.
- Blue and orange remain distinguishable for almost every form of color blindness, unlike red and green.
- Also check the contrast between text and background with the “Color converter”, which shows the WCAG level.
- For an interface, simulate a screenshot of each state: error, success, disabled.
Common problems and fixes
The simulation barely changes anything
If the image is mostly blues, grays or similar tones, the red-green forms change it little: that's a good sign. Try tritanopia.
Saving is slow
The image is processed at full resolution, pixel by pixel: allow one to a few seconds per simulation for a large photo.
The simulated colors look wrong
The simulation shows what gets confused, not an exact color: each color-blind person perceives a little differently.
Frequently asked questions
How many people are color blind?
About 8% of men and 0.5% of women see colors differently, most often confusing red and green. Out of 100 visitors to a website, several on average don't see colors the way you do.
Is the simulation reliable?
It is based on the Machado, Oliveira and Fernandes (2009) model, a scientific reference for simulating color vision. It gives a very good idea of the confusions, but each color-blind person perceives colors a little differently.
What does “strength of the milder forms” mean?
Anomalies (protanomaly, deuteranomaly…) are partial forms: the person sees the color, but less well. 100% is the full form, 60% a moderate form.
How do I fix an unreadable chart?
Don't rely on color alone: add labels, patterns or different shapes, and prefer color pairs that stay distinct, such as blue and orange.
Is my image uploaded to a server?
No, the simulation is computed pixel by pixel on your device.
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Still stuck?
Ask on the forum: the category, the tool, your device sheet and the test result will be filled in for you.