Color Contrast Requirements

Contrast is a measure of the difference in perceived "luminance" or brightness between two colors. This brightness difference is expressed as a ratio ranging from 1:1 (e.g. white on white) to 21:1 (e.g., black on a white). The visual presentation of text and images of text must have a contrast ratio of at least 4.5:1 with some exceptions.

Text (small and large)

• Small text (14 points or 11 pixels): A contrast ratio of at least 4.5:1 between the foreground and background colors.
• Large text (18 points or 14 pixels or larger): A contrast ratio of at least 3:1 between the foreground and background colors.

Text on images

• Text on images with a background that is part of the image: A contrast ratio of at least 3:1 between the foreground and background colors.
• Text on images with a background that is not part of the image: The same requirements as for small or large text, depending on the size.

If a text effect, such as an outline or a halo/aura, is used, the outline border or halo color must meet the contrast requirement.

Using a color contrast checker tool can help you quickly determine if your color combinations meet these standards.