Preview how an image, design, slide, chart or game UI looks to people with colour vision deficiency (colour blindness) — entirely in your browser. Colour vision deficiency affects roughly 1 in 12 men and 1 in 200 women, and makes certain colour combinations hard to tell apart. If your slides, transit maps, chart legends or friend-or-foe markers rely on colour alone, some people won't get the message. This tool lets you choose a vision type. Protanopia (red-weak) and deuteranopia (green-weak) are the common red-green types where red and green are easily confused; tritanopia (blue-weak) is the rarer blue-yellow type; and achromatopsia is total colour blindness, where everything looks monochrome. The severity slider then lets you move smoothly from a mild anomaly (anomalous trichromacy, a slight weakening) to full dichromacy (almost no perception of that colour). It works by applying a per-type colour transform to each pixel's red, green and blue, then blending with the original by the severity amount to reproduce the appearance. If two colours become hard to distinguish after simulation, consider raising the contrast, adding a difference in lightness, or adding text labels or patterns (hatching). Save the result as a PNG to share for team or client review. Load images by dropping, clicking to choose, or pasting from the clipboard. All processing happens in your browser — the image is never sent to any server or API, so it's safe to check internal documents or unreleased designs.