Sim Daltonism 4+

A window to color blindness

Michel Fortin

    • 5.0 • 72 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

5.0 out of 5
72 Ratings

72 Ratings

themilkman ,

Great app, incredibly useful if you're not colourblind

This app is an essential tool for any visual designer, allowing them to see how their decisions in terms of use of colours will impact usability for people with various colour deficiencies.

If you are not colourblind, it is very difficult to understand how your design choies affect people with colour dificiency, so this gives an insight into what others can and can't see, which can only make designs better in the end.

Developer Response ,

You have to authorize the app in System Preferences: Security and Privacy: Privacy tab: Screen Recording section. You might have missed the alert telling you that on first run.

Scarletclark ,

Superb tool

This is a godsend... needed to review the screen shot for a Excel tool for GPs, and was dreading having to compare every colour (which was looking like the only way). Because it filters the whole image it's easy to screenshot or show onscreen to developers why you need them to alter the colours. I've already recommended this to a number of people. It's also totally intuitive to use. Thanks for makiing it available

Deoxysnacher ,

Essential for research academics and designers

Amazing tool, really simple and intuitive that allows you to create informative and impactful research graphs and figures whilst being mindful of various colourblindness issues.

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 based on, for example, the features you use or your age. Learn More

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