Continuing our article series on accessibility requirements, Alternative Text or Alt-Text is an area that is often misunderstood. One of the first steps to web and document accessibility, providing accurate and appropriate descriptions for an image, can be critical to the overall goal of ensuring that content is accessible. Alt-text is often thought of as just an accessibility requirement. Still, beyond being read by screen readers to provide information on the meaning and content of a graphic image, it serves several other vital functions such as:<\/p>\n\n\n\n
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- Browsers will display the alt-text instead of the image if the file does not load or if the viewer is not viewing images.<\/li>\n\n\n\n
- Search engines will use the alt-text description to determine the content of the image.<\/li>\n<\/ul>\n\n\n\n
One best practice to consider is that the alt-text descriptions should be written by the document\u2019s original author, as they would know best why the image was included in the web content or document. <\/p>\n\n\n\n
In this article, we will focus on providing proper alt-text for documents<\/strong>, so only some of the WCAG 2.0 Guidelines below are applicable.<\/p>\n\n\n\n
Guideline 1.1 Text Alternatives: Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols, or simpler language.<\/strong><\/p>\n\n\n\n
Understanding Guideline 1.1<\/h2>\n\n\n\n
1.1.1 Non-text Content:<\/strong> All non-text content<\/a> presented to the user has a text alternative<\/a> that serves the equivalent purpose, except for the situations listed below. (Level A)<\/p>\n\n\n\n
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- Controls, Input: <\/strong>If non-text content is a control or accepts user input, it has a name<\/a> that describes its purpose. (Refer to Guideline 4.1<\/a> for additional controls and content requirements that accept user input.)<\/li>\n\n\n\n
- Time-Based Media: <\/strong>If non-text content is time-based media, then text alternatives at least provide descriptive identification of the non-text content. (Refer to Guideline 1.2<\/a> for additional requirements for media.)<\/li>\n\n\n\n
- Test: <\/strong>If non-text content is a test or exercise that would be invalid if presented in text<\/a>, then text alternatives at least provide descriptive identification of the non-text content.<\/li>\n\n\n\n
- Sensory: <\/strong>If non-text content is primarily intended to create a specific sensory experience<\/a>, then text alternatives at least provide descriptive identification of the non-text content.<\/li>\n\n\n\n
- CAPTCHA<\/a><\/strong>: <\/strong>If the purpose of non-text content is to confirm that a person rather than a computer is accessing content, then text alternatives that identify and describe the purpose of the non-text content are provided. And alternative forms of CAPTCHA using output modes for different types of sensory perception are provided to accommodate various disabilities.<\/li>\n\n\n\n
- Decoration, Formatting, Invisible: <\/strong>If non-text content is pure decoration<\/a>, is used only for visual formatting, or is not presented to users, then it is implemented in a way that it can be ignored by assistive technology<\/a>.<\/li>\n<\/ul>\n\n\n\n
Generally, the areas of the standard above that relate to document accessibility are the sections on Non-Text Content related to images and their intended meaning.<\/p>\n\n\n\n
One of the first determinations to be made is \u2013 why the image is used in the document? Does the image provide additional information or expand upon the text in the document?<\/p>\n\n\n\n
If the image does not provide any additional information but is merely used for decoration, then, in a PDF, it should be untagged and placed in an Artifact Container.<\/p>\n\n\n\n
The Artifact Container is not to be confused with the <Artifact> tag in a PDF\u2019s Tags tree. Currently, the use of the <Artifact> tag is not supported or properly recognized by assistive technologies.<\/p>\n\n\n\n
Note:<\/strong> This is for the current implementation of ISO 32000-1:2008. The PDF standard will be changing in the future, and when it does \u2013 and is supported \u2013 this technique will be changing.<\/p>\n\n\n\n
Now that any decorative images that do not convey any meaningful information have been untagged and thus ignored by screen readers, you can now focus on the remaining images. Writing meaningful alt-text is sometimes tricky, especially if you are not the document\u2019s original author and it is technical in nature.<\/p>\n\n\n\n
So, one of the first best practices is to have alt-text for images, charts, graphs, and other visual content written by the original author, who best understands the meaning of including the document\u2019s visual content.<\/p>\n\n\n\n
In the following example, the level of detail is dependent on the image and why it has been used.<\/p>\n\n\n\n
For the simple image below, a proper alt-text could be as simple as the following:<\/p>\n\n\n\n
\u201cWoman sitting at her computer, using CommonLook PDF<\/a> to remediate a PDF document for accessibility\u201d<\/em><\/p>\n\n\n
- Time-Based Media: <\/strong>If non-text content is time-based media, then text alternatives at least provide descriptive identification of the non-text content. (Refer to Guideline 1.2<\/a> for additional requirements for media.)<\/li>\n\n\n\n
- Controls, Input: <\/strong>If non-text content is a control or accepts user input, it has a name<\/a> that describes its purpose. (Refer to Guideline 4.1<\/a> for additional controls and content requirements that accept user input.)<\/li>\n\n\n\n
![\"Woman](\"https:\/\/allyant.com\/wp-content\/uploads\/2023\/01\/woman-using-commonlook-software.jpg\")
<\/figure>\n<\/div>\n\n\n![\"Screen](\"https:\/\/allyant.com\/wp-content\/uploads\/2023\/01\/commonlook-clarity-screen.png\")
<\/figure>\n<\/div>\n\n\n