Understanding Success Criterion 1.4.12: Text Spacing

Success Criterion 1.4.12 Text Spacing (Level AA): In content implemented using markup languages that support the following text style properties, no loss of content or functionality occurs by setting all of the following and by changing no other style property:

Exception: Human languages and scripts that do not make use of one or more of these text style properties in written text can conform using only the properties that exist for that combination of language and script.

Intent

The intent of this Success Criterion (SC) is to ensure that people can override text spacing to improve their reading experience. Each of the requirements stipulated in the SC's four bullets helps ensure text styling can be adapted by the user to suit their needs.

This SC focuses on the ability to increase spacing between lines, words, letters, and paragraphs. Any combination of these may assist a user with effectively reading text. As well, ensuring users can override author settings for spacing also signficantly increases the likelihood other style preferences can be set by the user. For example, a user may need to change to a wider font family than the author has set in order to effectively read text.

Author Responsibility

This SC does not dictate that authors must set all their content to the specified metrics. Rather, it specifies that an author's content has the ability to be set to those metrics without loss of content or functionality. The author requirement is both to not interfere with a user's ability to override the author settings, and to ensure that content thus modified does not break content in the manners shown in figures 1 through 4 in Effects of Not Allowing for Spacing Override.

Applicability

If the markup-based technologies being used are capable of overriding text to the Success Criterion's metrics, then this SC is applicable. For instance Cascading Style Sheet/HTML technologies are quite able to allow for the specified spacing metrics. Plugin technologies would need to have a built-in ability to modify styles to the specified metrics. Currently, this SC does not apply to PDF as it is not implemented using markup.

Examples of text that are typically not affected by style properties and not expected to adapt are:

  • Video captions embedded directly into the video frames and not provided as an associated caption file
  • Images of text

For this SC, canvas implementations of text are considered to be images of text.

User Responsibility

The ability to read and derive meaning from the overridden spacing rests with the user. If the increased spacing impacts those abilities, the user will adjust or they will return to the default view. Regardless, the user needs the flexibility to adjust spacing within the bounds set in the SC. Such changes may be acheived via user stylesheet, bookmarklet, extension, or application.

Effects of Not Allowing for Spacing Override

The following images show some types of failures when authors do not take into consideration that users may override spacing to the metrics specified in this Success Criterion.

Text Cut Off

The bottom portion of the words "Your Needs" is cut off in a heading making that text unreadable in Figure 1. It should read "We Provide a Mobile Application Service to Meet Your Needs."

Figure 1: Vertical text cut off is a failure.
Heading text truncated vertically.

In Figure 2 the last portion of text is cut off in 3 side-by-side headings. The 1st heading should read "A cog in the wheel." But it reads "A cog in the whe". Only half of the second "e" is visible and the letter "l" is completely missing. The 2nd heading should read "A penny for your thoughts". But it reads "A penny for your". The 3rd should read "Back to the drawing board." But it reads "Back to the drawi".

Figure 2: Horizontal text cut off is a failure.
3 side-by-side headings with truncated text.

Text Overlap

In Figure 3 the last 3 words "Groups and Programs" of the heading "Technologists Seeking Input from Groups and Programs" overlap the following sentence. That sentence should read, "You are invited to share ideas and areas of interest related to the integration of technology from a group or program perspective." But the words "You are invited to share ideas" are obscured and unreadable.

Figure 3: Overlapping text is a failure.
Heading text overlaps part of paragraph text.

Fixed Text

Text fails the SC when it is fixed and not able to be overridden to the Success Criterion's metrics.

Text that allows for overriding to the metrics passes. Line height must be able to adapt to 1.5 times the font size. Letter spacing must be able to adapt to 0.12 times the font size. Word spacing must be able to adapt to 0.16 times the font size. Spacing underneath paragraphs must be able to adapt to 2 times the font size.

Figure 4: Absolutely fixed text is a failure. Adaptable text passes.
Spacing Fail/Pass side-by-side comparison

Benefits

Examples

  1. Spacing can be overridden to the SC's metrics.
  2. Text fits within the bounds of its containing box without being cut off.
  3. Text fits within the bounds of its containing box without overlapping other boxes.

Related Resources

Resources are for information purposes only, no endorsement implied.

Research

The grounds for this SC are based on research. The metrics chosen as measures are based on the McLeish study. She ran from .04 to .25 em tests. McLeish found an increasing curve in reading speed of actual materials up to .25, but it started to flatten at .20. Previous studies that reported no improvement started at .5em. Right at the flat point. Wayne E. Dick, Ph.D. analyzed the McLeish study and translated from points. Dr. Dick recommended the metrics that the Working Group adopted.

Languages and Scripts

Roughly 480 different languages and scripts have been tested. Maximum spacing adjustments allowed by the SC were set on the following 3 pages:

  1. Languages in their own writing systems
  2. Online Encyclopedia of writing systems and languages – language names
  3. Universal Declaration of Human Rights (Article 1)

Results

No adverse effects occurred. The following are the specific findings:

Character Spacing
Individual characters in words remained intact though they were spaced a bit further apart.
Word Spacing
Words were spaced farther apart. In languages that do not have words (e.g. Japanese) applying word spacing had no effect. This is expected.
Line Height
Changing line height did not separate diacritics from characters, nor did it adversely impact ascenders or descenders.

As previously discussed, the ability to read text with adjusted spacing is a user responsibility. This is true no matter the language.

The SC's exception addresses cases where a text style property is not used in a language or script. In such cases, authors are only required to ensure relevant properties do not break the layout.

Other references

Techniques

Each numbered item in this section represents a technique or combination of techniques that the WCAG Working Group deems sufficient for meeting this Success Criterion. However, it is not necessary to use these particular techniques. For information on using other techniques, see Understanding Techniques for WCAG Success Criteria, particularly the "Other Techniques" section.

Sufficient Techniques

Advisory Techniques

Although not required for conformance, the following additional techniques should be considered in order to make content more accessible. Not all techniques can be used or would be effective in all situations.

Failures

The following are common mistakes that are considered failures of this Success Criterion by the WCAG Working Group.

Key Terms

image of text

text that has been rendered in a non-text form (e.g., an image) in order to achieve a particular visual effect

This does not include text that is part of a picture that contains significant other visual content.

A person's name on a nametag in a photograph.

style property

New

property whose value determines the presentation (e.g. font, color, size, location, padding, volume, synthesized speech prosody) of content elements as they are rendered (e.g. onscreen, via loudspeaker, via braille display) by user agents

Style properties can have several origins:

  • User agent default styles: The default style property values applied in the absence of any author or user styles. Some web content technologies specify a default rendering, others do not;
  • Author styles: Style property values that are set by the author as part of the content (e.g. in-line styles, author style sheets);
  • User styles: Style property values that are set by the user (e.g. via user agent interface settings, user style sheets)
text

sequence of characters that can be programmatically determined, where the sequence is expressing something in human language