Color Blind Simulator — Render Any Image Through CVD Vision

A color blind simulator answers the question screening tests cannot: what does my work look like to readers whose vision differs from mine? Drop in any JPG, PNG or WebP — a dashboard, a brand palette, a family photo — and this color blind simulator renders it through protanopia, deuteranopia and tritanopia models in real time. The color blind simulator exists for one job: showing you the gap between your colors and everyone else's. Every pixel is processed locally in your browser; the image never leaves your device.

Under the hood the color blind simulator applies the Machado, Oliveira & Fernandes (2009) severity-1.0 matrices in linear RGB — the model behind most professional accessibility checkers. Each mode re-transforms your ORIGINAL image pixels, never the already-simulated ones, so switching from deuteranopia to tritanopia never compounds errors. The implementation is vendored from the MIT-licensed dichroma project with the license preserved, so the color blind simulator you run here is auditable line by line.

The three color blind simulator modes

Protanopia models absent long-wavelength (L) cone input — reds darken toward brown or black and the classic red-green collapse follows. Deuteranopia models absent medium-wavelength (M) input — the most common inherited difference, where greens, reds and browns overlap. Tritanopia models absent short-wavelength (S) input — rare, and the blue-yellow world where teals meet pinks. One population-typical transform per mode: honest approximation, not any individual's exact sight.

Local-only by architecture

The color blind simulator reads your file with the browser's own APIs, draws it to an in-page canvas, and transforms pixels in JavaScript. There is no upload endpoint to send it to — you can watch the network tab stay empty. That is why the tool also works offline once the page is loaded, and why there is nothing to put in a privacy policy beyond "nothing is collected".

• Designers and product teams checking whether error states, charts and links survive red-green collapse — the WCAG-friendly habit.
• Developers verifying data visualizations: a palette that fails for 8% of male readers is a bug, not a style.
• Teachers building color-coded classroom materials that every student can read, whatever their vision.
• Photographers and marketers previewing how brand colors land across audiences — a quick color blind simulator pass before a campaign ships.
• Curious relatives and friends of color deficient people — the color blind simulator is the fastest empathy tool ever shipped in a browser tab.

A color blind simulator shows how images change under modeled vision; a screening test asks what YOU see. The two are complementary: designers use the simulator on their artifacts, and individuals use tests on themselves. If you arrived here wondering about your own vision, take the color blind test first, then come back and look at these plates through each simulated mode — the pairing explains more than either alone. The reverse colour blindness test experiment on this site is built on the same engine.

• 1Test the artifacts where color carries meaning: status colors, charts, maps, forms, game UI.
• 2Check text-on-background pairs too — the color blind simulator applies to everything in the image, not just charts.
• 3Fix by adding redundancy: labels, patterns, icons or luminance differences, then re-simulate.
• 4Download the simulated PNG and view it beside the original — a side-by-side comparison catches what quick mode-toggling in the color blind simulator hides.