🔴 Protanopia Simulator
See how an image or palette looks with protanopia, a red-weak color-vision deficiency, all processed on your device.
Choose an image to see the original and simulated versions side by side. It never leaves your device.
Machado, Oliveira & Fernandes (2009) matrices in linear-sRGB. Approximates average CVD perception. 🔒 Images processed on-device, never uploaded.
How the protanopia simulator works
Each pixel or swatch is linearised and multiplied by the published Machado (2009) protanopia matrix, then converted back to sRGB, with a severity slider for milder protanomaly. The transform models the loss of the red-sensitive (L) cone, so red light contributes far less perceived brightness, reds darken and slide toward the greens and browns they get confused with. Severity at 100% is the full dichromat matrix; lower settings blend original and simulated pixels to approximate protanomaly. Images are processed on a canvas and never uploaded.
Protanopia (red-weak) darkens reds and confuses them with greens and browns. Because reds appear dimmer, red warning text on a dark background can nearly vanish, worth testing directly.
Frequently asked questions
What is protanopia?
Protanopia is a red-green color-vision deficiency where the red-sensitive (L) cones are absent. Reds look darker and are easily confused with greens, browns and blacks.
How is it different from deuteranopia?
Both are red-green deficiencies, but protanopia specifically dims reds (red appears much darker), whereas deuteranopia affects greens more and keeps brightness closer to normal.
What should I check for?
Red text or icons on dark backgrounds (they can become very low-contrast) and any red/green distinction. Add non-color cues where meaning depends on red.
Is my image private?
Yes. It is processed on a canvas in your browser and never uploaded.
Can I adjust severity?
Yes, the slider interpolates toward full protanopia to approximate protanomaly (partial red-weakness).
How common is protanopia?
Red-weakness in all its forms (protanopia plus protanomaly) affects around 1-2% of men, less than deuteranopia but still worth testing, especially because it dims reds so strongly. It is very rare in women.
What is the practical thing to check under protanopia?
Anything where red carries meaning against a dark or green backdrop: red error text, red alert badges, red-vs-green chart lines. Because reds lose brightness, they can drop below usable contrast, pair red with a shape, icon, or lighter tint so the meaning survives.
Why does protanopia darken reds so much?
The red-sensitive (L) cone contributes most of the perceived brightness of red light. With it absent, red stimulates the remaining cones only weakly, so a pure red looks dim and muddy rather than vivid. That is why red-on-black text, which relies on the red being bright, can nearly vanish for someone with protanopia, a problem deuteranopia does not share as strongly.
How do I make reds work for protanopia?
Shift important reds toward orange or add lightness so they do not go dim, and never depend on a red/green distinction alone. Back up colour with icons, labels or shapes, and check red text against its background in the contrast checker, since the effective brightness of red is what drops under protanopia.