Around one in twelve men and a smaller share of women live with some form of colour vision deficiency, and a design that relies on red versus green alone can be unreadable to them. This simulator applies the three most common deficiencies, protanopia, deuteranopia, and tritanopia, to an image you upload, transforming its pixels with the standard simulation matrices so you can see the image roughly as someone with that vision would. It is a design check, not a medical tool: the matrices approximate perception, they do not reproduce any individual’s experience exactly. Used before publishing, it catches the classic failure, a chart whose series differ only by red and green, while there is still time to add labels, patterns, or direct annotation. Running the check on a finished design takes a minute and can be the difference between a chart everyone can read and one that silently excludes people.
Quick Answer: Upload an image, choose a colour blindness type, and see the simulated version.
Free Online Tool
Color Blindness Simulator
See your design through different eyes, before publishing.
How to Use the Color Blindness Simulator
- Upload the image or design you want to check.
- Choose protanopia, deuteranopia, or tritanopia.
- Press Simulate to transform the image.
- Compare the result with the original.
- Fix any information that disappears, then simulate again.
Key Features
- Simulates protanopia, deuteranopia, and tritanopia.
- Works on your own uploaded image.
- Standard colour-transformation matrices.
- Downloadable simulated PNG for sharing with a team.
- Private local processing with no uploads.
Best Practices and Tips
- Check charts and maps first; they are where colour-only encoding causes the most harm.
- If two colours become identical under simulation, they were never a safe pair to distinguish data.
- Add direct labels, patterns, or shapes alongside colour so information survives any simulation.
- Test all three types, not just one; a palette that survives protanopia can still fail tritanopia.
- Simulate early in design, when changing a palette is cheap, rather than after launch.
Common Mistakes to Avoid
- Treating the simulation as an exact replica of someone’s vision; it is an approximation for design checking.
- Testing only one deficiency type and assuming the others behave the same.
- Fixing a palette by eye without re-running the simulation to confirm the fix.
- Relying on colour alone for errors, success, and warnings in interfaces.
Frequently Asked Questions
What are protanopia, deuteranopia, and tritanopia?
They are the three main types of dichromatic colour vision: protanopia is the absence of red-sensitive cones, deuteranopia the absence of green-sensitive cones, and tritanopia the absence of blue-sensitive cones. Each shifts colour perception differently, which is why a design must be checked against all three, not just red-green types.
How accurate is the simulation?
It uses widely published transformation matrices that approximate how colours map under each deficiency. It is accurate enough to catch design failures, but it cannot reproduce any individual’s exact perception, which varies with the severity and type of their condition.
What should I do if my design fails?
Do not rely on colour alone: add labels, icons, patterns, or direct values so the information exists in another channel. Then choose a palette whose colours remain distinct under simulation, and re-run the check to confirm.
Does this diagnose colour blindness?
No. It simulates deficiencies on images for design purposes and cannot test anyone’s vision. A proper diagnosis requires an eye-care professional and standardised vision tests.
Is my image uploaded?
No. The image is transformed on a canvas in your browser and the download is generated locally. Nothing is sent to any server.