Alt Text and Image Description
From document design to web publishing to our daily interactions via social technologies, visual media is a primary, even preferred, mode of delivering and accessing information. However, for accessibility users, images, diagrams, charts, maps, icons, etc. can inhibit or interrupt, rather than enhance, access to content.
Where a set of stairs might pose a barrier for someone with limited physical mobility, these types of media are often inaccessible to visually impaired users, as well as those with dyslexia, cognitive impairments, and age-related macular degeneration.[i]
To see and make sense of visual media, accessibility users require a text-based alternative, in the form of alternative text or image description.
What are Image Descriptions and Alt Text?
Alternative text is written text that provides meaningful description of visual media to accessibility users who are visually impaired or who require an alternative text format. Image descriptions provide much more detailed description than alt text, allowing the user to learn more about what is in the image, beyond alt text. Alt text gives the user a short condensed description, while long image descriptions provide explicit detail. Supplying text alternatives of visual media can significantly increase access to content for a wide range of users.
Alt text performs multiple functions:
- Since it is read by screen readers in place of an image, it allows the content and purpose of the image to be accessible to people with visual and cognitive disabilities.
- Is shown in place of an image on a website when an image file is not loaded or a user chooses not to view images.
- Providing content and description for images that can contribute to SEO results .
As proficiency in accessibility has increased, alt text has been included as a feature within other content authoring tools, such as MS Office applications, Adobe PDF, and others. And image descriptions are being used in mediums that do not natively support alt text as an attribute to augment or replace visual content.
It is important to note, though often referring to image media, alt text is also commonly used to help situate accessibility users to other forms of complex content, such as tables, charts, diagrams, etc., that may include textual elements, but due to their complexity pose challenges for accessibility users and assistive technologies.
Alt Text and Search Engine Results
Alt text provides web accessibility to visually-impaired users, but what is alt text’s use in SEO? Does it really affect your rankings and, if so, how?
Search engines are very efficient at scanning text content, but they do not understand visual elements. If visual elements are properly indexed, they will be displayed in relevant search results. What this means is that if images do not have alt text, search engines are not able to understand them and therefore won’t display them in search results. Because images can be a large part of some search engine results, this could result in a massive missed opportunity.
Why are Image Descriptions and Alt Text Important?
Consider a process diagram demonstrating a new business workflow with icons marking teams and colors denoting benchmarks; or a graphic of a water cycle in a student textbook that makes use of arrows of varying shades and sizes to depict key aspects of the cycle.
Accessibility users with limited or complete vision impairment will not be able to derive the necessary meaning implied by visual cues, such as shape, size, positioning, or color that are inherent in visual media. These and other users rely on assistive technologies (e.g., screen readers or Braille readers), which are unable to programmatically access non-text content.
Without text alternatives for visual content, those who are visually impaired will likely miss or misunderstand information conveyed through these inaccessible visual forms.
Do all Visual Media Require a Description?
No, not all visual media require alternative text descriptions. Though one must be cautious when determining whether visual content is primary vs decorative content. Digital documents and environments are often littered with decorative image media. There is good reason to discuss and debate how or why visual content may or may not inform a user’s meaningful experience of content.
However, all visual content requires assessment and some level of alt text attribute controlling. Even when images are purely decorative — meaning, the image does nothing to inform the user’s understanding of the primary content in meaningful, clear, or necessary ways — the image must be hidden from assistive technologies by applying a “null” value. (In HTML this is an empty value for @alt [alt=””]). In popular document applications, there are settings to mark such content as background, presentational, or decorative.
Alt text ensures that visual content will be discoverable by assistive technologies. But by also hiding unnecessary content, it ensures that accessibility users will not be disrupted by unnecessary images.
What is the Difference Between Alt Text and Long Descriptions?
In many cases, descriptions can be satisfied in a couple of sentences (either as an “Alt” attribute value or as a long description following the visual content as text or a caption). Precision is key in authoring alternative text. The goal is to provide accurate, meaningful, and legible descriptions that enable the accessibility user to follow the logical flow of content without becoming distracted or confused. The format and length of alternative text typically depends on the document’s medium or integrated alt tools, the type of source content, and, as in all cases, the end-user’s needs. In the case of images containing text, it is considered best practice to provide all textual elements. The placement of long form text alternatives depends on the document medium and user needs.
Visual content can also require long form textual alternatives. This is most often the case where the content is primary rather than supplementary. For example, a technical illustration within a textbook would require a long description that represents all textual elements (e.g., terms, definitions, measurements, etc.) along with a carefully crafted description of the design features. These types of descriptions require an attention to audience and application to inform the level of detail and language used.
Real Life Example for Use of Image Descriptions
Suzanne is a blind high school student who uses a screen reader to navigate through her coursework and the internet. Her courses all have online textbooks and learning materials that include visual media, such as graphs, diagrams, and illustrations. She encounters problems when websites are not properly coded or don’t have alt text on images or the alt text is insufficient. Unfortunately, some of these websites are inaccessible and it takes her a lot of time to read all the page text from top to bottom without navigation cues. Sometimes she gets trapped in parts of a webpage, isn’t able to move to different area, and must quit the page entirely. When these visual materials are referenced in class or within her exams, she is unable to follow along or respond as expected.
Laws and Acts Regarding Image Descriptions
Various Acts and Laws cover the need for alt text and image descriptions to ensure equal access and communications with people who are blind or visually impaired, including:
- 21st Century Communications and Video Accessibility Act (CVAA)
- Individuals with Disabilities Education Act (IDEA)
- Section 508 & Section 504 of the Rehabilitation Act
- Americans with Disabilities Act (ADA)
These cover public and private education both for K-12 and higher ed, virtual education, healthcare services, government services, government employment settings, various public transportation services, legal and law enforcement services, and many other venues.
Accessibility References
“The Web Content Accessibility Guidelines (WCAG) were developed through the W3C process in cooperation with individuals and organizations around the world, with a goal of providing a single shared standard for web content accessibility that meets the needs of individuals, organizations, and governments internationally.” [ii]
WCAG 2.1 success criteria applying to alt text include:
How can I be Sure My Image Descriptions are Compliant and Useful?
The best way to know that your alt text and image descriptions are compliant is to work with an accessibility partner who will evaluate them against Section 508 specifications and WCAG. SeeWriteHear offers comprehensive evaluation and testing services required to achieve and maintain compliance. We can write or remediate your alt text to make your assets accessible.
Reference Articles
- Making Images Readable to Meet ADA Compliance
- Website Accessibility Under Title II of the ADA
- Complex Images
[i] Inclusive Publishing. Accessible Content for Everyone. https://inclusivepublishing.org/consumer/.
[ii] W3C, Web Accessibility Initiative. Web Content Accessibility Guidelines (WCAG) Overview: Introduction. https://www.w3.org/WAI/standards-guidelines/wcag/.