Decorative vs Meaningful Images: a Technical Guide

Understanding Image Classifications for WCAG Compliance

Decorative images provide no additional context or information beyond what is already present in the copy of the webpage of PDF. These images are used solely to enhance the visual appearance of the page, such as an icon of a water drop or a stock photo of a classroom. In most industries, decorative images make up the majority of images typically because writing copy is the first step in creating a webpage or PDF. 

When decorative images are treated as meaningful it unnecessarily creates noise for users who rely on assistive technology, reducing the clarity of their experience and potentially creating a frustrating experience.

Meaningful images provide additional context or convey critical information not found in the body copy. These images serve a functional purpose and require alternative text that describes their relevance. For example, a chart depicting water treatment efficiency over time is meaningful because it communicates information not explicitly covered in the surrounding copy (unless, of course, the numbers and figures are included in surrounding copy). 

When meaningful images are treated as decorative it creates an inequitable experience where sighted users have access to information that screen reader users do not.

Decision Framework for Image Classification

To determine if an image requires alt text, apply this straightforward assessment:

• Does the image convey information not present in the surrounding text?
• Would removing the image reduce understanding of the content?
• Does the image perform a specific function (like a chart or diagram)?
• Does the image trigger an action or represent a specific state?

If the answer is “yes” to any of these questions, the image should be treated as meaningful and alternative text should be added.

If the answer is “no” to all questions, the image should be treated as decorative and properly marked as such in the code (e.g., using null alt attributes in HTML or “Artifact” designation in PDFs).

Complex Cases:Some images may contain both decorative and meaningful elements. For example, a technical diagram might have a decorative border but contain crucial information not conveyed elsewhere on the page. In such cases, focus the alternative text on the meaningful content while ignoring purely decorative elements.

Practical Example: Consider a page about biosolids with an image of a Terragator spreading biosolids:

• Scenario 1 – Meaningful Image: If the page copy discusses how biosolids are produced and their benefits, but does not reference a Terragator or application methods, the image is meaningful. It PROVIDES ADDITIONAL, UNIQUE INFORMATION that enhances understanding. The image requires alt text, such as “A large, drivable machine called a Terragator spreads biosolids by spraying them from one side while driving through an agricultural field.”
• Scenario 2 – Decorative Image:If the page copy explicitly explains how biosolids are applied to fields using a Terragator, the image becomes decorative because it reinforces the content WITHOUT ADDING NEW INFORMATION. Alternative text would be redundant since users of assistive technology already have access to this information.

Legal and User Experience Implications

WCAG Success Criterion 1.1.1 (Non-text Content) requires that “all non-text content that is presented to the user has a text alternative that serves the equivalent purpose.” While this criterion can be subject to interpretation, providing alt text only when images contribute additional information not present in surrounding content aligns with both the letter and spirit of WCAG guidelines.

This approach:

1. Reduces unnecessary screen reader verbosity;
2. Maintains informational equity between sighted and non-sighted users;
3. Prevents confusion from redundant information.

From a compliance standpoint:

1. Omitting alt text for purely decorative images is explicitly supported by WCAG documentation;
2. Providing alt text for images that merely illustrate already-stated information creates an unnecessarily burdensome experience, potentially undermining the core accessibility principles of perceivable and usable content;
3. Omitting alt text for images that contribute new information creates an inequitable experience where sighted users have access to information that screen reader users do not.

Best Practices

1. Evaluate each image in its full context with all surrounding elements, not in isolation;
2. Consider the user experience for people using assistive technologies;
3. When in doubt, test the page’s readability with and without the image;
4. Document your image classification decisions, noting specifically why images were determined to be decorative or meaningful;
5. Conduct periodic sampling reviews of image classifications to ensure team alignment;
6. Remember that over-describing decorative images can be as problematic as under-describing meaningful ones.

This framework helps ensure both WCAG compliance and an optimal experience for all users, regardless of how they access the content.

This guide provides general information and should not be construed as legal advice. Organizations should consult with qualified legal professionals for specific guidance on compliance requirements.