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Understanding Success Criterion 1.4.4 [Resize text]

1.4.4 [begin add] Text (but not images of text)[end add] [begin delete]Visually rendered text[end delete] can be resized without assistive technology up to 200 percent and down to 50 percent without loss of content or functionality. [2164] (Level AA)

Intent of this Success Criterion

The intent of this success criterion is to ensure that visually rendered text [begin add](text characters that have been displayed so that they can be seen [vs. text characters that are still in data form such as ASCII]) [1978] [end add] can be scaled successfully so that it can be read directly by people with mild visual disabilities, without requiring the use of assistive technology such as a screen magnifier. Users may benefit from scaling all content on the Web page, but text is most critical.

The scaling of content is primarily a user agent responsibility. User agents that satisfy UAAG 1.0 Checkpoint 4.1 allow users to configure text scale. The author's responsibility is to create web content that does not prevent the user agent from scaling the content effectively. Authors may satisfy this success criterion by verifying that content does not interfere with user agent support for resizing text, or by providing direct support for resizing text or changing the layout. An example of direct support might be via server-side script that can be used to assign different style sheets.

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The author cannot rely on the user agent to satisfy this success criterion for HTML content if users do not have access to a user agent with zoom support. For example, if they work in a environment that requires them to use IE 6 or Firefox.

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If the author is using a technology whose user agents do not provide zoom support, the author is responsible to provide this type of functionality directly or to provide content that works with the type of functionality provided by the user agent. If the user agent doesn't provide zoom functionality but does let the the user change the text size, the author is responsible for ensuring that the content remains usable when the text is resized. [2034]

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Content satisfies the success criterion if it can be scaled up to 200%, that is, up to twice the width and height. Authors may support scaling beyond that limit, however, as scaling becomes more extreme, adaptive layouts may introduce usability problems. For example, words may be too wide to fit into the horizontal space available to them, causing them to be truncated; layout constraints may cause text to overlap with other content when it is scaled larger; or only one word of a sentence may fit on each line, causing the sentence to be displayed as a vertical column of text that is difficult to read.

The working group feels that 200% is a reasonable accommodation that can support a wide range of designs and layouts, and complements older screen magnifiers that provide a minimum magnification of 200%. Above 200%, zoom (which resizes text, images, and layout regions and creates a larger canvas that may require both horizontal and vertical scrolling) may be more effective than text resizing. Assistive technology dedicated to zoom support would usually be used in such a situation and may provide better accessibility than attempts by the author to support the user directly.

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50% was chosen to provide symmetry in the ranges. The ability to scale in both directions is desirable. [2112]

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Specific Benefits of Success Criterion 1.4.4:

  • This success criterion helps people with low vision by letting them increase text size in content so that they can read it.

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    The ability to scale down 50% is a benefit for individuals with tunnel vision and close vision. It also benefits individuals who use some screenreaders and magifiers in that it allows them to get more content on the page without requiring them to scroll. [2112]

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Examples of Success Criterion 1.4.4

Related Resources

Resources are for information purposes only, no endorsement implied.

Techniques and Failures for Success Criterion 1.4.4 [Resize text]

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. The techniques listed only satisfy the success criterion if all of the WCAG 2.0 conformance requirements have been met.

Sufficient Techniques

  1. G142: Using a technology that has commonly-available user agents that support zoom

  2. Ensuring that text containers resize when the text resizes AND using measurements that are relative to other measurements in the content by using one or more of the following techniques:

  3. Providing controls on the Web page that incrementally change the size of the text (future link)

  4. Providing options within the content to switch between layouts that use a variety of font sizes (future link)

Common Failures Identified by the Working Group

The following are common mistakes that are considered failures of Success Criterion 1.4.4 by the WCAG Working Group.

Additional Techniques (Advisory) for 1.4.4

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.

  • Providing large fonts by default (future link)

  • Avoiding the use of text in raster images (future link)

  • Using page-percent for container sizes (future link)

  • Avoiding scaling font sizes smaller than the user-agent default (future link)

    Note: The author won't actually know the font size, but should avoid percentage scaling that results in less than 100%

  • Avoiding justified text (future link)

  • Providing sufficient inter-line and inter-column spacing (future link)

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    Providing different sizes for non-text content when it can not have an equivalent accessible alternative (future link) [2269]

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Key Terms

assistive technology (as used in this document)
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hardware and/or software that acts as a user agent, or along with a mainstream user agent, to provide services to meet the requirements of users with disabilities that go beyond those offered by the mainstream user agents [2140]

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a user agent that[begin delete] both[end delete]:

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  1. provides services to meet the requirements of users with disabilities that go beyond those offered by the mainstream user agents. Such services include alternative presentations (e.g., as synthesized speech or magnified content), alternative input methods (e.g., voice), additional navigation or orientation mechanisms, and content transformations (e.g., to make tables more accessible), and

  2. [begin change]may rely[end change] [begin delete]usually relies[end delete] on services (such as retrieving Web content and parsing markup) provided by one or more other mainstream user agents. Assistive technologies communicate data and messages with mainstream user agents by using and monitoring APIs

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Note 1: Services provided by assistive technology include alternative presentations (e.g., as synthesized speech or magnified content), alternative input methods (e.g., voice), additional navigation or orientation mechanisms, and content transformations (e.g., to make tables more accessible). [2140] [2270]

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Note 2: Assistive technologies often communicate data and messages with mainstream user agents by using and monitoring APIs. [2270]

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Note 3: The distinction between mainstream user agents and assistive technologies is not absolute. Many mainstream user agents provide some features to assist individuals with disabilities. The basic difference is that mainstream user agents target broad and diverse audiences that usually include people with and without disabilities. Assistive technologies target narrowly defined populations of users with specific disabilities. The assistance provided by an assistive technology is more specific and appropriate to the needs of its target users. The mainstream user agent may provide important services to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles. [2171]

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Note 4: In this definition, user agents are user agents in the general sense of the term. That is, any software that retrieves and presents Web content for users. The mainstream user agent may provide important services to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles.

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Note 5: Mainstream user agents may also provide services directly that meet the requirements of users with disabilities.

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Note 6: This definition is based on User Agent Accessibility Guidelines 1.0 Glossary.

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Example: Examples of assistive technologies that are important in the context of this document include the following:

  • screen magnifiers, and other visual reading assistants, which are used by people with visual, perceptual and physical print disabilities to change text font, size, spacing, color, synchronization with speech, etc. in order to improve the visual readability of rendered text and images;

  • screen readers, which are used by people who are blind to read textual information through synthesized speech or braille;

  • text-to-speech software, which is used by some people with cognitive, language, and learning disabilities to convert text into synthetic speech;

  • voice recognition software, which may be used by people who have some physical disabilities;

  • alternative keyboards, which are used by people with certain physical disabilities to simulate the keyboard[begin add] (including alternate keyboards that use headpointers, single switches, sip/puff and other special input devices.)[end add];

  • alternative pointing devices, which are used by people with certain physical disabilities to simulate mouse pointing and button activations.

text

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