Color-Blindness Simulator

About Color-Blindness Simulator

The Color-Blindness Simulator is a free, browser-based accessibility tool that shows how a screenshot, UI mockup, chart, or any image looks to people with color-vision deficiency. You drop in an image and it renders a live before/after compare slider — "Normal vision" on one side and the simulated view on the other — across four modes: protanopia (no red), deuteranopia (no green), tritanopia (no blue), and achromatopsia (no color). The simulation is pure canvas math using published RGB transform matrices (Machado/Brettel coefficients), with no external library, so everything runs locally in your browser — your image is never uploaded and there's no signup.

How to use Color-Blindness Simulator

1. Drop a UI screenshot or image onto the upload area, or click to browse (any image/* file).
2. Pick a type of color-blindness from the segmented control: Protanopia, Deuteranopia, Tritanopia, or Achromatopsia (Deuteranopia is selected by default).
3. Drag the compare slider to wipe between 'Normal' vision and the simulated view of your image.
4. Switch between the four modes to check each one, watching for information that disappears or two states that become indistinguishable.
5. Where color alone carries meaning, add a non-color cue — an icon, label, or pattern — then re-check in the simulator.

Frequently asked questions

Is my image uploaded to a server?

No. The image is loaded and simulated on a canvas entirely in your browser using local matrix math — nothing is ever uploaded or sent anywhere.

Is it free and do I need an account?

Yes, it's completely free with no signup, account, or watermark.

Which types of color-blindness can it simulate?

Four: protanopia (no red), deuteranopia (no green), tritanopia (no blue), and achromatopsia (no color / total grayscale). You switch between them with one tap on the segmented control.

How accurate is the simulation?

It applies widely-used published RGB transform matrices (Machado/Brettel-style coefficients) per pixel. This is a solid design-review approximation, not a clinical diagnosis of any individual's vision.

What file formats and sizes does it accept?

Any standard image your browser can decode (PNG, JPG, WebP, GIF, etc.). Large images are scaled down to a maximum of 1400px on the longest side for fast preview.

Can I download or save the simulated image?

This tool is a side-by-side preview and compare tool, not an exporter — there's no download button. It's designed for checking accessibility in the moment, so if two states look identical for a color-blind viewer, you add a non-color cue like an icon, label, or pattern.

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