How do I see how my chart looks to someone who is red-green color blind?

Upload a JPEG, PNG or WebP, then pick Deuteranopia or Protanopia (or the milder Deuteranomaly or Protanomaly). Drag the compare slider to reveal the original on the left. Red and green items that look alike need a non-color cue.

Which types of color blindness can I simulate?

Eight views: Normal vision, Protanopia, Deuteranopia, Tritanopia, Protanomaly, Deuteranomaly, Tritanomaly and Achromatopsia. The simulation applies a 3x3 color matrix to every pixel, so it approximates, not replaces, testing with real viewers.

Which image formats work, and is there a size limit?

JPEG, PNG and WebP are accepted. Images are scaled down so the longest edge is at most 1200 px, so a large photo is simulated and downloaded at that reduced size. If loading fails, the file may be corrupt or unsupported.

Does my image get uploaded to a server?

No. The image is drawn to a canvas in your browser and the color transform runs on your own device, with no model or network request involved.

How do I save the simulated image?

Choose the color vision type you want, then press Download simulated image. The file is a PNG of the simulated version at the processed size (up to 1200 px on the longest edge), not the original resolution.

Yes. Every tool is free to use, with no account and no credit card. The work runs on your device rather than on our servers, which is what keeps it free to run.

Are my files uploaded?

No. Your files are opened and processed inside your browser and are not sent to LibraTool. Some tools first download a processing engine or AI model to your browser; that download contains no data of yours.

Does it work on mobile?

Yes. It runs in current mobile browsers on iOS and Android, with nothing to install. Very large files can be slow or run out of memory on a phone, so use a computer for those.

👁️

Free Color Blindness Simulator

See how your design looks to people with color vision deficiencies. Simulates protanopia, deuteranopia, tritanopia, achromatopsia, and milder anomalies.

File size depends on your deviceFiles stay privateNo login requiredFree forever

Works offline once loaded

Drop a file here, or click to browse

JPG, PNG, WebP, HEIC, HEIF · processed on your device

or press Ctrl+V to paste from your clipboard

Browse files

Your files never leave your device. All processing happens locally in your browser.

Upload a design, infographic, or photo to see how it appears to people with color vision deficiencies. Especially useful for: chart designers, UX designers, and accessibility audits.

Common uses

Audit Charts and Graphs for Color BlindnessTest data visualizations to ensure they're understandable for the ~8% of men with color vision deficiency.
Audit UI Designs for AccessibilityCheck your app UI screenshots in CVD modes — make sure all state indicators are visible to everyone.
Test Print Designs for Color AccessibilityPosters, infographics, and printed materials all benefit from a CVD check before printing.
Photographer Color EducationPhotographers can use the simulator to understand how their viewers might perceive color in their work.
Teach About Color Vision DeficiencyDemonstrate to students, designers, or developers what CVD actually looks like.

How It Works

Color vision deficiency (CVD) is simulated using Brettel-Viénot color transformation matrices — the standard algorithm used in accessibility tools.

1
You drop an image
The image is loaded into a canvas in your browser. Pixels are downsized for performance (max 1200 px on the longest edge).
2
A 3×3 color transform is applied to every pixel
Each CVD type has a specific matrix. For deuteranopia (green-blind), red and green channels get mixed in a way that mimics what people with only L+S cones perceive.
3
The transformed image displays alongside the original
Switch between CVD types to see how the same image looks for the ~8% of men with some form of color vision deficiency.

Your image stays in your browser. Even the simulation math runs locally on your CPU — no server, no API, no upload.

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Check whether two colors meet WCAG AA and AAA contrast standards for accessibility. Live preview at multiple text sizes with automatic suggestions when contrast is too low.

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Free Color Blindness Simulator

Common uses

How It Works

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Frequently Asked Questions