About the Colour Contrast Analyser

This native application (available for both Windows and Mac) allows you to evaluate the color visibility and contrast of foreground/background color combinations. It provides an initial pass/fail assessment against WCAG 2.0 color contrast success criteria.

In addition, the Colour Contrast Analyser provides functionality to simulate certain visual conditions such as dichromatic color blindness (protanopia, deuteranopia, tritanopia) and cataracts. Note: the image simulation features are currently not available in the Mac version.

Details

The Color Contrast Analyser was developed to facilitate the assessment of color combinations against WCAG 2.0:

Guideline 1.4 Distinguishable: Make it easier for users to see and hear content including separating foreground from background.

  • Guideline 1.4.3: Contrast (Minimum) The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for the following: (Level AA)

    • Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 3:1;
    • Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement.
    • Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.
  • Guideline 1.4.6: Contrast (Enhanced) The visual presentation of text and images of text has a contrast ratio of at least 7:1, except for the following: (Level AAA)

    • Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 4.5:1;
    • Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.

The Colour Contrast Analyser uses the following formula to determine contrast:

L = 0.2126 * R + 0.7152 * G + 0.0722 * B

where R, G and B are defined as:

  • if RsRGB <= 0.03928 then R = RsRGB/12.92 else R = ((RsRGB+0.055)/1.055) ^ 2.4
  • if GsRGB <= 0.03928 then G = GsRGB/12.92 else G = ((GsRGB+0.055)/1.055) ^ 2.4
  • if BsRGB <= 0.03928 then B = BsRGB/12.92 else B = ((BsRGB+0.055)/1.055) ^ 2.4

and RsRGB, GsRGB, and BsRGB are defined as:

  • RsRGB = R8bit/255
  • GsRGB = G8bit/255
  • BsRGB = B8bit/255

Acknowledgements

The Colour Contrast Analyser was developed by JUn in collaboration with Steve Faulkner (The Paciello Group, Europe). Mac version developed by Cédric Trévisan (The Paciello Group, Europe).

For feedback and suggestions, or to provide additional translations, please contact Steve Faulkner (sfaulkner@paciellogroup.com).

Terms of use

The Colour Contrast Analyser is freeware. It is made available for both personal and commercial use to help you determine the accessibility of your web content.

This work is licenced under a Creative Commons License Creative Commons Attribution No Derivatives 3.0 License

THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED WARRANTY. IN PARTICULAR, THE PACIELLO GROUP DOES NOT MAKE ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE RELIABILITY, QUALITY, OR MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. ADDITIONALLY, THE PACIELLO GROUP DOES NOT GUARANTEE THAT USE OF THIS SOFTWARE WILL ENSURE THE ACCESSIBILITY OF YOUR WEB CONTENT OR THAT YOUR WEB CONTENT WILL COMPLY WITH ANY SPECIFIC WEB ACCESSIBILITY STANDARD.