Color Blindness Simulator
See a design as 8% of men do.
Color Blindness Simulator shows an image or a colour pair as it appears with protanopia, deuteranopia, tritanopia and achromatopsia, using published colour-vision transformation matrices. It flags the pairs that collapse into one another. Pixels are transformed in a canvas on the page, so the image never leaves your device.
Loading Color Blindness Simulator…
Runs entirely on your device. No file or text you enter here is uploaded. How to verify it.
How to use Color Blindness Simulator
- Drop an image, a screenshot or a set of colours.
- Compare the simulations side by side.
- Fix any pair that becomes indistinguishable.
Questions about Color Blindness Simulator
How common is colour vision deficiency?
About 8% of men and 0.5% of women of northern European descent. Deuteranomaly — reduced green sensitivity — is by far the most common form, which is why red/green status indicators fail so often.
How do I design around it?
Never rely on hue alone. Add a shape, an icon, a label or a pattern so the information survives when colour does not. Differences in lightness survive all the common deficiencies; differences in hue do not.
How accurate is the simulation?
It uses the standard Brettel/Viénot linear transformations, which model dichromacy well. Anomalous trichromacy — the milder and more common form — is a spectrum this cannot represent exactly, so treat the output as a strong indicator rather than a literal view.
Does my image leave the device?
No. The file is decoded and redrawn in a canvas inside the page, every pixel is transformed there, and each download is written from that same canvas. Nothing is uploaded and no account is required. Once the page has been visited, it also runs with the network switched off.
What image sizes and formats work?
Anything the browser can decode — PNG, JPEG, WebP, GIF and, on current browsers, AVIF. The five side-by-side previews are scaled down to 600 pixels wide so they render quickly, while each download is generated at the original resolution. The practical ceiling is your device's memory, not an upload limit.
Is Color Blindness Simulator really free, with no limits?
Yes. There is no account, no daily cap, no file-size tier and no watermark, because there is no server cost to recover. The site is funded by clearly disclosed partner recommendations on the Partners page, never by metering the tools.
Are my files or text uploaded when I use Color Blindness Simulator?
No. Everything is processed by JavaScript running in your browser, on your device. You can verify it: open your browser's developer tools, switch to the Network tab, and use the tool. You will see no request carrying your data — because there is nowhere for it to go.