Color Blindness Simulator
Choose an image to see how it looks with the main types of colour blindness.
Your picture is processed inside this page and never uploaded.
What this tool does
Choose an image or screenshot and the tool shows it side by side as it appears with protanopia (no red cones), deuteranopia (no green cones), tritanopia (no blue cones) and achromatopsia (no colour). It applies the Machado et al. 2009 transformation in linear RGB. Download any of the simulated views as a PNG.
Applies a colour vision deficiency transformation to every pixel of your picture.
Shows the original and four simulated views at once.
How to use it
- Choose an image or screenshot.
- Compare the simulated views with the original.
- Look for areas where different colours become hard to tell apart.
- Download a simulated view if needed.
Why use this simulator
Shows your picture side by side as it appears with protanopia, deuteranopia, tritanopia and achromatopsia, using the published Machado et al. (2009) matrices in linear RGB. Roughly 1 in 12 men and 1 in 200 women have some form of colour vision deficiency. Charts, maps, status colours and buttons that rely on red versus green can become unreadable, and seeing the problem is the quickest way to fix it.
Why we built it
We built the colour blindness simulator on the published Machado matrices and show the original beside four simulated views. Check text colours with the contrast checker and pick accessible colours with the palette generator.
Who this tool is for
- Designers and developers testing accessibility
- Product teams reviewing dashboards
- Teachers explaining colour vision
When to use it
- Checking a chart, map or dashboard.
- Testing a UI that uses red and green status colours.
- Reviewing branding and illustrations.
- Explaining the issue to a team.
How it works
Each pixel is converted from sRGB to linear light, multiplied by a 3×3 matrix modelling the missing cone type, and converted back. Protanopia (no L cones) and deuteranopia (no M cones) are the common red-green forms; tritanopia (no S cones) is rare. Achromatopsia is shown as luminance only.
The matrices model complete absence of the cone type at full severity. Many people have a milder form (anomalous trichromacy), so the view is a worst case.
This is a simulation to guide design, not a diagnosis, and screens differ. Use shape, labels and contrast as well as colour.
What you give it, and what you get back
| Item | Details |
|---|---|
| Image | JPG, PNG, WebP or any browser-readable image. |
| Output | The original plus four simulated views, and a PNG download of one. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| The simulation looks subtle | The picture has little red, green or blue distinction. | Try a chart or a status colour palette. |
| Large images are scaled | Views are limited to 900 pixels on the longest side. | Crop to the area of interest. |
| Transparent PNG shows black | Transparent pixels have no colour. | Place it on a background first. |
Assumptions and limitations
- Models full dichromacy only.
- Different screens and viewing conditions change the appearance.
- Not a clinical tool.
Frequently asked questions
What is colour blindness?
A reduced ability to distinguish certain colours, most often red and green, caused by a missing or altered cone type in the eye.
What is the most common type?
Red-green deficiencies - deuteranomaly and protanomaly - are the most common.
How accurate is the simulation?
It uses published research matrices and is a good guide, but individuals vary and screens differ.
How do I make a design accessible?
Do not rely on colour alone; add labels, patterns and sufficient contrast.
Is my image uploaded?
No. It is processed in your browser.
Is my text or file sent anywhere?
No. Everything runs in your browser and nothing leaves the page.