See your designs through colour-blind eyes

Frequently asked questions

What does the colour blindness simulator do?

It transforms an image to approximate how someone with a colour vision deficiency sees it. You can compare the original and simulated versions side by side, with a split slider, hold to flip back to the original, or see every type at once in a grid. It is a quick way to check whether a design, chart, or photo still reads clearly for the roughly 1 in 12 men and 1 in 200 women who see colour differently.

Which types can it simulate?

Deuteranopia and protanopia (the two red-green types), tritanopia (blue-yellow), achromatopsia (total colour blindness, shades of grey) and blue-cone monochromacy (only the blue cones work). The severity slider shows the milder forms: below 100% the names change to deuteranomaly, protanomaly, tritanomaly and so on.

How accurate is it?

Red-green types use the Machado, Oliveira and Fernandes (2009) matrices, with the paper's own matrix for each severity step. Tritanopia uses the Brettel, Viénot and Mollon (1997) model; partial tritanomaly is a straight blend with normal vision, so treat it as approximate. Blue-cone monochromacy is a simple grey from the blue-cone response and ignores the rods. All of it is calculated in linear light. This is a good approximation for design review, but individual experiences of colour blindness vary, so no simulation is exact.

Can I check my webcam or a live view?

Yes. As well as uploading an image, you can switch on your camera to see the world around you simulated in real time, and save a snapshot at the camera's full resolution. The video is processed entirely in your browser and never leaves your device. The camera stops when you press Stop or leave the page.

How can I add images, and which files work?

Upload, drag and drop, or paste (Ctrl or Cmd + V) a PNG, JPG, WebP, GIF, BMP, AVIF or SVG picture. HEIC photos from an iPhone are not supported by most browsers, so the page points you to the HEIC to JPG converter. You can also type colours as hex codes in the Palette checker instead of using an image.

What do the design checks tell me?

In the Palette checker, enter hex colours and the tool flags pairs that look different to typical vision but fall below a CIEDE2000 colour difference of 8 once simulated, for each of the five types. It also shows the WCAG contrast ratio of a text and background pair with typical vision and under each type. The Corrected view is a simple daltonize approximation that shifts lost colour differences into channels the viewer can still use. It is a design aid, not a medical correction.

Are my images uploaded?

No. Every image and camera frame is processed locally in your browser, in a background worker, and nothing is uploaded or stored. It's free with no sign-up. You can download the result as a PNG at the original size (up to the browser's canvas limit) or the preview size; the file name includes the type and severity. The share link holds only the vision type, severity and palette, never an image. Your last settings are remembered in this browser.