How to use
- Upload an image, screenshot, or design mockup (JPG, PNG, WebP, or GIF).
- Choose a vision type — Protanopia, Deuteranopia, Tritanopia, or Achromatopsia.
- Compare the normal-vision and simulated views side by side.
- Cycle through each type, then download the simulated image to drop into a report or share with your team.
What each type means
Colour vision relies on three types of cone in the retina. Each kind of colour blindness corresponds to one of them working differently or not at all:
- Protanopia — the long-wavelength (red) cones are missing. Reds look dark and muddy, and red/green pairs collapse.
- Deuteranopia — the medium-wavelength (green) cones are missing. This is the most common type; greens and reds again become hard to separate.
- Tritanopia — the short-wavelength (blue) cones are missing. Blues and yellows blur together. It’s rare.
- Achromatopsia — no usable colour cones at all, so the world is seen in shades of grey. Very rare, but a useful worst-case check.
Why simulate at all?
If a design conveys meaning through colour alone — a green “success” pill next to a red “error” pill, a chart whose only legend is hue — then anyone whose colour vision differs may miss that meaning entirely. Running the design through each simulation makes those failures obvious, so you can add a redundant cue: a label, an icon, a shape, or simply more contrast. Pairing this with a contrast checker covers most colour-accessibility issues before launch.
Private by design
Every pixel is transformed locally in your browser via the Canvas API using the standard CVD simulation matrices. Your image is never uploaded, so the preview is instant and your files stay private.