Protanopia Simulator

Protanopia Simulator renders a color beside the same color as a protanopic viewer would see it, using the protanopia matrix and printing the resulting hex value.

What is Protanopia Simulator?

Protanopia Simulator shows a color twice: as it is, and as a protanopic viewer would see it. The two swatches are drawn large and side by side, which keeps the comparison to a single glance, and the hex value of the simulated result is printed underneath so the conversion can be recorded.

Protanopia is the absence of the long-wavelength cone that carries red, and it differs from the other red-green deficiency in one respect that matters for design:

• Reds lose saturation and darken noticeably, which means a red that was already dark can become nearly black.
• Red and green converge toward a similar olive tone, so the hue axis between them largely closes.
• Blues and yellows stay comparatively intact, since they depend on the short-wavelength cone.
• Because reds also drop in luminance, a protanopic viewer can find a dark red harder to see than a deuteranopic viewer would, which is the practical difference between the two pages.

The simulated swatch comes from a fixed three-by-three matrix applied directly to the 8-bit red, green and blue channels. Its first row is 0.567 red plus 0.433 green, its second is 0.558 red plus 0.442 green, and its third is 0.242 green plus 0.758 blue, with the outputs clamped back into the 0 to 255 range and formatted as hex. The matrix is an approximation of how protanopia is usually modelled rather than an exact colorimetric transform, and it is applied at full strength with no way to ask for a partial result.

The narrowness of the page is worth being explicit about.

• One deficiency only. The other complete type needs its own page, and the image mode lives elsewhere.
• A single color at a time, so a palette is checked entry by entry.
• No image or screenshot input.
• Full-strength conversion, with nothing to represent a mild reduction in red sensitivity.
• The output describes the model, not any individual viewer.

Reach for this page when a design leans on red, and especially when red is used against a dark surface or as a status color. Check the simulated swatch for two properties in particular: whether it has drifted toward the other colors in the set, and whether it has lost enough lightness to disappear against its background. Because this deficiency darkens reds as well as shifting them, a red that reads as vivid to you can be both duller and dimmer here, and that combination is what usually breaks an alert color.

Read the page as a red cone simulation rather than as a palette review, because that is exactly what it is: one input color, one conversion and one printed result. The protanopia hex value below the simulated swatch is the useful artefact, letting you compare the converted color against the rest of your set without leaving the page. What it will not do is tell you whether a cvd protanopia viewer can still tell two colors apart, since that depends on the pair rather than on either color taken alone.

How to use Protanopia Simulator

1. Set the color you want converted in the swatch field.
2. Compare the two large swatches, with the original on the left and the protanopic simulation on the right.
3. Read the hex value under the simulated swatch and note how far it has moved in lightness, not only in hue.
4. Check that value against the dark surfaces it might sit on, since protanopia darkens reds rather than merely dulling them.

When to use Protanopia Simulator vs related tools

Use the protanopia simulator when red carries meaning and you need to see how far a red moves once the long-wavelength cone is removed, which is the case it handles differently from the other red-green page. For the partial form, see the protanomaly simulator; for the other complete red-green deficiency, the deuteranopia simulator; for all four deficiencies and the image simulation in one place, the color blindness simulator; and for text colors that survive the same conversion, the accessible color pair finder.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.

Frequently asked questions about Protanopia Simulator