Techniques for WCAG 2.0

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# G183: Using a contrast ratio of 3:1 with surrounding text and providing additional visual cues on focus for links or controls where color alone is used to identify them

## Applicability

Colored text when color alone is used to convey information such as words that are links in a paragraph

This technique relates to:

- Success Criterion 1.4.1 (Use of Color)
  - How to Meet 1.4.1 (Use of Color)
  - Understanding Success Criterion 1.4.1 (Use of Color)

## Description

The intent of this technique is to provide a redundant visual cue for users who may not be able to discern a difference in text color. Color is commonly used to indicate words that are links within a paragraph or other block of text. For example, scattered words in text may be hypertext links that are identified only by a difference in color with surrounding text. This technique describes a way to provide additional cues on hover and focus so that users who may have difficulty perceiving color differences or have low vision can identify them.

With this technique, a relative luminance (lightness) difference of 3:1 or greater with the text around it can be used if additional visual confirmation is available when a user points or tabs to the link. Visual highlights may, for example, take the form of underline, a change in font style such as bold or italics, or an increase in font size.

While using this technique is sufficient to meet this success criteria, it is not the preferred technique to differentiate link text. This is because links that use the relative luminance of color alone may not be obvious to people with black/white color blindness. If there are not a large number of links in the block of text, underlines are recommended for links.

Note 1: This technique is about the use of color in addition to luminosity. In this technique, the contrast ratio refers to the contrast between a link and the words around it. In Success Criterion 1.4.3 and 1.4.6, contrast ratio refers to the contrast between a word and its background. The difference is that because this technique is about the ability for users to tell the difference (a noticeable difference) between different pieces of text whereas the contrast ratio used in success criterion 1.4.3 and 1.4.6 is about the readability of the text with its background for different color and vision disabilities.

Note 2: If an author wants to use the color portion of this technique (i.e., using different colors for the words where the colors have sufficient contrast with each other) and the author also wants to conform to SC 1.4.3 (contrast of both words with their backgrounds) the following colors can be used. (e.g., black text in a paragraph on a white background with the links shown as one of the colors in the list below.)

Note 3: If assistive technology or Web browsers at some point all provide an option to underline all links on Web pages for users, this could be used instead of an author-provided link highlighting mechanism.

## Examples

### Example 1: Colors that would provide 3:1 contrast with black words and 4.5:1 contrast with a white background

Refer to Links with a 3:1 contrast ratio with surrounding text

### Example 2

The hypertext links in a document are medium-light blue (#3366CC) and the regular text is black (#000000). Because the blue text is light enough, it has a contrast of 3.9:1 with the surrounding text and can be identified as being different than the surrounding text by people with all types of color blindness, including those individuals who cannot see color at all.

## Resources

Resources are for information purposes only, no endorsement implied.

- Contrast Analyser – Application

- Contrast Ratio Analyser - online service

- Colour Contrast Analyser - Firefox Extension

## Related Techniques

- G14: Ensuring that information conveyed by color differences is also available in text
- G122: Including a text cue whenever color cues are used
- G145: Ensuring that a contrast ratio of at least 3:1 exists between text (and images of text) and background behind the text
- G182: Ensuring that additional visual cues are available when text color differences are used to convey information

## Tests

### Procedure

1. Locate all instances where color alone is used used to convey information about text.

2. Check that the relative luminance of the color of the text differs from the relative luminance of the surrounding text by a contrast ratio of at least 3:1.

3. Check that pointing (mouseover) to the link causes a visual enhancement (such as an underline, font change, etc.)

4. Check that moving keyboard focus to the link causes a visual enhancement (such as an underline, font change, etc.)

### Expected Results

- Checks #2, #3, and #4 are all true.

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