Color Blindness Simulator

Your dashboard uses a green dot for healthy and a red one for broken, the chart has two lines in neighbouring shades, and the error message is red on grey. For roughly one in twelve men, much of that reads as the same colour. Drop a screenshot or an image file in the area above and compare the original with the simulation side by side, then download the result as PNG to attach to a ticket or a pull request.

Every pixel goes through a 3x3 matrix over the RGB channels, in the spirit of the Brettel and Machado models. Two things almost nobody mentions: the simulation represents dichromacy, the complete absence of one cone type, which is the severe end of the range, while the most common cases are anomalous and milder; and the matrix is applied straight to gamma encoded sRGB rather than linear light. Read the output as an approximation, not a measurement.

Use it to hunt for information carried by hue alone: wherever two areas merge, add a label, an icon, a dash pattern or a difference in lightness. The achromatopsia mode doubles as a greyscale test and is the fastest way to spot weak contrast. It does not measure contrast ratio or text size, so it is no substitute for a WCAG check. The image is read and drawn in your browser with no upload, and the preview is capped at 600 px wide.