Color Blindness Simulator

Color blindness (color vision deficiency, or CVD) is a condition where the eyes do not perceive certain colors normally. It is usually inherited and affects the three types of cone cells in the retina that respond to red, green, and blue light. Color blindness is much more common in men than women — roughly 1 in 12 men and 1 in 200 women experience some form of it. Most people with color blindness see the world in a fairly normal way and only struggle to distinguish specific color pairs like red/green or blue/purple.

There are 7 types simulated in this tool. The three main forms are protanopia (no red cones — reds appear dark or black), deuteranopia (no green cones — greens appear brownish), and tritanopia (no blue cones — blues appear greenish). Achromatopsia is the complete absence of color vision, producing only shades of gray. The three milder forms are protanomaly, deuteranomaly, and tritanomaly, where red, green, or blue cone sensitivity is reduced rather than completely missing. Deuteranomaly is by far the most common, affecting roughly 5% of men.

The simulator applies scientifically derived Brettel, Viénot & Machado (1997) transformation matrices to every pixel of your image. Each matrix mathematically models how a person with that specific deficiency perceives red, green, and blue channels, then remaps the pixel colors accordingly. For anomalies, the matrix reduces channel sensitivity; for dichromat types (protanopia, deuteranopia, tritanopia), it collapses the affected channel entirely. Achromatopsia maps every pixel to its grayscale luminance.

Click the upload area (or drag and drop a file) to load any JPEG, PNG, WebP, GIF, or BMP image. The original and a simulated preview appear side by side instantly. Use the seven simulation type buttons to switch between deficiencies, and the preview re-renders automatically. When you are happy with a result, click Download Simulated Image to save it as a PNG. You can also use the Single Color Simulation mode to test any hex color across all seven deficiency types without uploading an image.

Yes — completely free, no registration required, and 100% private. All image processing, color simulation, and rendering happens locally in your browser using HTML5 Canvas and JavaScript. Your images are never uploaded to any server, and nothing is stored, tracked, or shared. This makes it safe to use with sensitive design files and client work.

Yes. Once the page has loaded, every feature — image upload, simulation, color picking, and download — runs entirely in your browser with no network connection required. You can disconnect from the internet and keep simulating images, testing colors, and exporting PNG results without any interruption.

Upload a screenshot of your UI, chart, or infographic and switch between the seven simulation types to spot problem areas. Look for colors that become indistinguishable, text that loses contrast, and chart elements that merge together. Use the Single Color Simulation to check specific brand or status colors, and combine it with WCAG contrast guidelines for a stronger audit. The Ishihara-style swatches give a quick at-a-glance reference for how common test colors shift under each deficiency.