Source code
Revision control
Copy as Markdown
Other Tools
---
myst:
substitutions:
image1: |-
```{image} 28369550088_617db0d6f2_m.jpg
:alt: Colorful image of a cat's face, without modification```
image2: |-
```{image} colorcat_protanopia.png
:alt: Colorful image of a cat's face, with protanopia simulation```
image3: |-
```{image} colorcat_deuteranopia.png
:alt: Colorful image of a cat's face, with deuteranopia simulation```
image4: |-
```{image} colorcat_tritanopia.png
:alt: Colorful image of a cat's face, with tritanopia simulation```
image5: |-
```{image} colorcat_achromatopsia.png
:alt: Colorful image of a cat's face, with achromatopsia simulation```
image6: |-
```{image} colorcat_contrastloss.png
:alt: Colorful image of a cat's face, with contrast loss simulation```
---
# Color vision simulation
The simulator in the {doc}`Accessibility Inspector <../index>` in Firefox Developer Tools lets you see what a web page would look like to users with various forms of *color vision deficiency* (better known as "color blindness"), as well as *contrast sensitivity loss*.
"Color blindness" is a bit of a misnomer, since most people with these disorders can see colors, but do not see all of the distinctions that people with normal color vision can see; color vision deficiencies affect perception across the color spectrum, not only of specific colors like red or green. Color vision deficiencies affect about 8% of men, and 0.5% of women. The most common forms of color blindness (commonly lumped together as "red-green color blindness") affect more men than women, because they are due to a mutation in a gene in the X chromosome, which men usually have only one copy of.
Contrast sensitivity loss can be caused by cataracts, glaucoma, diabetic retinopathy, and other disorders of the retina; it can be age-related, congenital, or due to an injury.
:::{note}
This feature depends on webrender, an experimental featurethat is not enabled by default on all platforms. You can force-enablewebrender by settingthe preference `gfx.webrender.all` to `true` using the [Firefox Configuration Editor](https://support.mozilla.org/en-US/kb/about-config-editor-firefox) (note that if webrender is enabled by default on your platform, the setting has no effect.
:::
The current color simulation option may be selected from the **Simulate** menu as shown.
```{image} accessibily_color_simulation_menu.jpg
:alt: 'Simulate menu in Accessibility panel. Used for selecting the simulation mode:
: None, Protanopia (no red), Deuteranopia (no green), Tritanopia (no blue), Achromatopsia
: (no color), Contrast loss'
:class: center
```
The following table shows a colorful image of a cat's face, and what it looks like in the each of the simulations.
```{eval-rst}
.. list-table::
:widths: 50 50
:header-rows: 1
* - Simulation
- Image displayed
* - None (Choose this to return to normal display)
- .. image:: 28369550088_617db0d6f2_m.jpg
* - Protanopia (no red)
- .. image:: colorcat_protanopia.png
* - Deuteranopia (no green)
- .. image:: colorcat_deuteranopia.png
* - Tritanopia (no blue)
- .. image:: colorcat_tritanopia.png
* - Achromatopsia (no color)
- .. image:: colorcat_achromatopsia.png
* - Contrast loss
- .. image:: colorcat_contrastloss.png
```
:::{note}
The simulation transformation matrices are based on the paper: [A Physiologically-based Model for Simulation of Color Vision Deficiency](https://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/CVD_Simulation.html), Gustavo M. Machado, Manuel M. OliveiraLeandro A. F. Fernandes, IEEE Transactions on Visualization and Computer Graphics, Volume 15 (2009).
:::
## See also
- [WCAG success criterion 1.4.11: Non-text contrast](https://www.w3.org/TR/WCAG21/#non-text-contrast)