Sim Daltonism 4+

A window to color blindness

Michel Fortin

    • 4.9 • 35 Ratings
    • Free



From the perspective of a color blind person, some colors are impossible to distinguish. Sim Daltonism lets you visualize colors as they are perceived with various types of color blindness.

Move the Sim Daltonism window over something on the screen and see what it looks like with a color blindness. With this app you can check the accessibility of websites and other user interfaces, make your visual designs better for color blind people, or just play around to better understand how various color blindness types affect color perception.

The Filter Window

The Sim Daltonism window acts as a filter for what is under it. You can click inside and manipulate windows from other apps that are located under it.

But you can change this so the filter window follows the mouse pointer, displaying the area around it. This makes it possible to view the filtered image alonside the unfiltered one.


Sim Daltonism is fast enough to filter a video in real time or to have many filter windows active simultanously.

If needed, you can reduce or increase the refresh speed to save energy or improve responsiveness.

Simulated Vision

Sim Daltonism can simulate the vision of many forms of color blindness:

• Deuteranopia (no green cones)
• Deuteranomaly (anomalous green cones)
• Protanopia (no red cones)
• Protanomaly (anomalous red cones)
• Tritanopia (no blue cones)
• Tritanomaly (anomalous blue cones)
All colors
• Monochromacy
• Partial monochromacy

Note that the colors shown are only an approximation. Color blindness varies from person to person and the simulator cannot represent everyone’s vision. Many other factors can affect the results, such as the automatic white point calibration of the camera. Nevertheless, Sim Daltonism is a good tool to better understand color blindness.

Sim Daltonism is open source and is also available for iOS.

What’s New

Version 2.0.5

• Corrected an issue with the filter where some saturated blues would incorrectly become purple.

Ratings and Reviews

4.9 out of 5
35 Ratings

35 Ratings

NullLifeException ,

New Transparent Window mode is awesome!

I used a previous version of this application a while back to learn what my websites looked like with various types of colour blindness. I hard heard about it on a software podcast about accessibility. While it got the point across, that version was a little clunky with some issues with the infinite windows effect when you moved the mouse near the preview window. It was still functional but a little too jaring to be something that I'd open often.

I downloaded 2.0 today to show the colour blindness effects on a website to another software developer and was absolutely delighted with the Transparent Window mode. I certainly wasn't expecting clicks to work through the window, either, but the illusion was flawless. I really enjoyed using the new version and will probably use it much more often now. Thank you for making accessible web and software development easier.

One thing I kind of miss from the past version (if I remember right) was that there was a percentage of the population listed in the menu next to the type of colour blindness. That was a very nice piece of context for educating people on colour blindness.

App Privacy

The developer, Michel Fortin, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer's privacy policy.

Data Not Collected

The developer does not collect any data from this app.

Privacy practices may vary, for example, based on the features you use or your age. Learn More

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